Process for Particleboard Manufacture

ABSTRACT

Improved particleboard and methods for fabricating improved particleboard (e.g., natural fiber/material-based particleboard) are disclosed. More particularly, the present disclosure provides systems/methods for fabricating particleboard (e.g., formaldehyde-free particleboard) utilizing natural fibers/materials (e.g., lignocellulosic materials), wherein the particleboard has improved performance characteristics and/or mechanical properties. Methods for fabricating fiber-reinforced biocomposites (e.g., natural fiber-reinforced wheat gluten biocomposites) are disclosed. For example, systems/methods for fabricating particleboard from lignocellulosic materials (e.g., coconut materials), along with a binder material (e.g., wheat gluten), are provided. In general, the fiber or lignocellulosic material is treated with sodium hydroxide and/or a silane coupling agent as an adhesion promoter to enhance interfacial adhesion between the fiber and the binder. For example, (3-triethoxysilylpropyl)-t-butylcarbamate (MISO) (a masked isocyanate functional silane) was utilized to improve interfacial adhesion between the binder and the natural fibers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation patent application that claimspriority benefit to a co-pending non-provisional patent applicationentitled “Process for Particleboard Manufacture,” which was filed onOct. 12, 2012, and assigned Ser. No. 13/651,017, which in turn claimsthe benefit of U.S. Provisional Application No. 61/546,615, filed Oct.13, 2011, all of which are herein incorporated by reference in theirentireties.

BACKGROUND

1. Technical Field

The present disclosure relates to particleboard and methods forfabricating particleboard (e.g., from natural fibers/materials, such ascoconut-based materials) and, more particularly, to particleboard (e.g.,formaldehyde-free particleboard) utilizing natural fibers/materials(e.g., lignocellulosic materials), wherein the particleboard hasimproved performance characteristics and/or mechanical properties.

2. Background Art

In general, particleboard is an engineered panel product manufacturedfrom wood particles (e.g. wood chips, sawmill shavings and/or sawdust)and/or other lignocellulosic particles and fibers (e.g. hemp, kenaf,jute and/or cereal straw), which are typically pressed and bondedtogether using a binder (see, e.g., Wallenberger et al., Natural fibers,plastics and composites, Chapter 14: Uses Of Natural Fiber ReinforcedPlastics, Kluwer Academic Pub. (2004) 249-53). It is noted that whilesome in the industry may generally differentiate some classes of bondedboards such as, for example, particleboard, fiber-board and others, theterm particleboard is used in the present disclosure to include theproducts (e.g., particleboard, bonded-board, fiber-board, etc.) that maybe fabricated utilizing the systems and methods of the presentdisclosure, as described below.

Particleboard is often used for indoor products including cupboards,built-in furniture, and shelving, as well as for many other constructionapplications or the like. In general, urea-formaldehyde (UF) andphenol-formaldehyde (PF) resins are typical binders used by theparticleboard industry due to a variety of reasons (e.g., low cost, easeof use, a variety of curing conditions, low cure temperature, shortcuring time, water solubility, resistance to microorganisms and toabrasion, thermal properties, strength and water resistance) (see, e.g.,El-Wakil et al., Modified Wheat Gluten As A Binder In Particleboard MadeFrom Reed, Journal of Applied Polymer Science, (2007) 106(6), 3592-99;and Maloney, T. M., The Family Of Wood Composite Materials, ForestProducts Journal (1996) 46(2), 19-26).

However, UF and PF resins are generally neither eco-friendly nor safedue to health effects of exposure to formaldehyde emissions (see, e.g.,Marutzky, R., Release Of Formaldehyde By Wood Products, WoodAdhesives—Chemistry And Technology, Marcel Dekker, Inc., (1989) 307-87;Henderson, J. T., Volatile Emissions From The Curing Of Phenolic Resins,TAPPI Journal (1979) 62(8), 93-96; Meyer et al., Formaldehyde ReleaseFrom Wood Products: An Overview, ACS symposium series 316: FormaldehydeRelease From Wood Products, (1986), 1-16; Groah, W. J., FormaldehydeEmissions: Hardwood Plywood And Certain Wood Based Panel Products, ACSsymposium series 316: Formaldehyde release from wood products, (1986)12-26; Baumann, M. G. D., Aldehyde Emission From Particleboard AndMedium Density Fiberboard Products, Forest Products Journal, (2000)50(9), 75-82; Mo, X. et al., Compression And Tensile Strength Of LowDensity Straw-Protein Particleboard, Ind. Crops Prod. (2001) 14, 1-9).

Moreover, formaldehyde-based adhesives are derived from generallyunsustainable petrochemicals. Therefore, formaldehyde-free adhesivesfrom renewable resources have been developed for the wood compositesindustry. In general, natural adhesives based on proteins such as soyprotein, wheat gluten, and milk casein are an attractive alternative foran environmentally friendly binder for particleboard production (see,e.g., Lei, H. et al., Gluten Protein Adhesives For Wood Panels, J. ofAdhesion Science and Tech. (2010), 24, 1583-1596; Nordqvist et al.,Comparing Bond Strength And Water Resistance Of Alkali-Modified SoyProtein Isolate And Wheat Gluten Adhesives, Int'l J. of Adhesion &Adhesives (2010) 30, 72-79; Khosravi et al., Protein-Based Adhesives ForParticleboards, Industrial Crops and Products (2010) 32, 275-83; Sun etal., Bio-Based Polymers And Composites, Elsevier Inc., (2005) 292-368;Hettiarachchy et al., Alkali-Modified Soy Protein With Improved AdhesiveAnd Hydrophobic Properties, J. Am. Oil Chem. Soc. (1995) 72, 1461-64;Wang et al., Low Density Particleboard From Wheat Straw And Corn Pith,Ind. Crops Prod. (2002) 15, 43-50; Zhong et al., Wet Strength And WaterResistance Of Modified Soy Protein Adhesives And Effects Of DryingTreatment, J. Polym. Environ. (2003) 11, 137-44; Leiva et al.,Medium-Density Particleboards From Rice Husks And Soybean ProteinConcentrate, J. Appl. Polym. Sci. (2007) 106, 1301-06).

In general, wheat gluten (WG) is a complex protein derived from wheat,and has been investigated for potential use in food and non-foodapplications. In the last decades, environmental concerns about anincrease in non-degradable plastic waste have generated interest inbiopolymers from renewable natural sources. WG-based plastics canpotentially be used to substitute conventional petroleum-based plasticsdue to their non-toxicity, large-scale availability, low cost,biodegradability, and environmentally friendly properties (see, e.g.,Bietz et al., Properties And Non-Food Potential Of Gluten, Cereal FoodsWorld (1996) 41, 376-82).

However, some of the plastics made from WG are brittle, and generallyabsorb water after being processed. Some approaches to improve themechanical properties and water resistance of WG have been developed.For example, the addition of additives such as synthetic and naturalfibers to reinforce WG is one approach to tailor the mechanicalproperties of WG plastics. Some advantages of natural fibers overtraditional reinforcing and man-made fibers (e.g. glass, carbon,aluminum oxide and Kevlar) are their low cost, low density, goodspecific mechanical properties, high toughness, non-abrasive behaviorduring processing, enhanced energy recovery, and biodegradability (see,e.g., Avella et al., Eco-Challenges of Bio-Based Polymer Composites,Materials (2009) 2, 911-25).

In general, these advantages make the natural fibers a potentialreplacement for the conventional reinforcement materials in composites.However, some of the potential drawbacks of the natural fibers in thecomposites are incompatibility with many hydrophobic polymer matrices,and relatively high moisture absorption (see, e.g., Saheb et al.,Natural Fiber Polymer Composites: A Review, Advances in Polymer Tech.(1999) 18(4), 351-63). Therefore, some chemical surface treatments havebeen considered to modify the fiber surface properties, typicallyresulting in improved fiber-matrix adhesion. Some of these chemicaltreatments include de-waxing, alkali treatment, peroxide treatment,acetylation, acrylation, benzoylation, treatment with various couplingagents, and others (see, e.g., Mohanty et al., Surface Modifications OfNatural Fibers And Performance Of The Resulting Biocomposites: AnOverview, Composite Interfaces (2001) 8(5), 313-43).

In general, the thiol groups (—SH) of cysteine in the WG protein play arole in adhesion. At a high temperature, a thiol/disulfide interchangereaction typically occurs, thus cross-linking the protein to form athree dimensional network (see, e.g., Schofield et al., The Effect OfHeat On Wheat Gluten And The Involvement Of Sulphydryl-DisulphideInterchange Reactions, J. Cereal Sci. (1983) 1, 241-53; Fernandes etal., Theoretical Insights Into The Mechanism For Thiol/DisulfideExchange, Chem. Eur. J. (2004) 10, 257-66; Pommet et al., Study Of WheatGluten Plasticization With Fatty Acids, Polymer (2003) 44, 115-22).

Thus, during particleboard preparation by hot-press molding, thecross-linking reaction of WG typically occurs. In general, duringhot-press molding, some phenolic hydroxyl groups of lignin in woodparticles or lignocellulosic materials are oxidized to form quinines.The thiol groups in WG can then react with the quinines through theMichael addition reaction, typically resulting in adhesion between woodparticles or lignocellulosic materials and the WG adhesives (see, e.g.,Takasaki et al., Formation Of Protein-Bound 3,4-DihydroxyphenylalanineAnd 5-S-Cysteinyl-3, 4-Dihy-Droxyphenylalanine As New Cross-Linkers InGluten, J. Agric. Food Chem. (1997) 45, 3472).

In general, coconut fiber and coconut coir pith (coco peat) are derivedfrom coconut husks. Coconut fiber (CCF) is lignocellulosic fibertypically extracted from the husk of coconut fruit obtained from coconutpalm trees (Cocos nucifera), which are abundantly available in tropicalcountries. The coconut pith is the particulate generally obtained afterlong fibers are removed from the coconut husk. Coconut fiber can be usedto make, for example, rope, yarn, floor mats, mattresses and brushes,while the pith material is typically manufactured into industrialadsorbents, composting material or plant growing systems. However, asmall percentage of the coconut fiber and coconut pith is consumed forconventional uses, and much of it still remains unused.

In general, CCF possesses many advantages. For example, it isinexpensive, moth-proof, generally resistant to fungi and rot, noteasily combustible, flame-retardant, it provides excellent insulationagainst temperature and sound, and it is amenable to chemicalmodification. Moreover, CCF is tough and durable. In general, it is themost ductile fiber amongst the natural fibers, capable of taking about4-6 times more elongation than other fibers (see, e.g., Ali, M., CoconutFibre—A Versatile Material And Its Applications In Engineering, SecondInt'l Conference on Sustainable Construction Materials and Tech. (2010)Main Vol. 3, Paper 13, 1441-54).

CCF has been used as reinforcement in order to modify the properties ofmany polymers, such as polyester, polyester amide, polyacrylate,polypropylene, linear low density polyethylene (LLDPE), high impactpolystyrene (HIPS), polyurethane, poly-3-hydroxy butyrate co-valerate(PHBV), starch/ethylene vinyl alcohol copolymers blend, and naturalrubber.

See, e.g., Rout et al., The Influence Of Fiber Surface Modification OnThe Mechanical Properties Of Coir-Polyester Composites, PolymerComposites (2001) 22(4), 468-76; Rout et al., The Influence Of FibreTreatment On The Performance Of Coir-Polyester Composites, CompositesScience and Tech. (2001) 61 1303-10; Hill et al., Effect Of FiberTreatments On Mechanical Properties Of Coir Or Oil Palm Fiber ReinforcedPolyester Composites, J. of Applied Polymer Science (2000) 78(9),1685-97; Hill et al., The Effect Of Environmental Exposure Upon TheMechanical Properties Of Coir Or Oil Palm Fiber Reinforced Composites,J. of Applied Polymer Science (2000) 77(6), 1322-30; Varma et al., CoirFibers, J. of Reinforced Plastics and Composites (1985) 4(4), 419-29;Abdul Khalil et al., Effect Of Acetylation And Coupling Agent TreatmentsUpon Biological Degradation Of Plant Fiber Reinforced PolyesterComposites, Polymer Testing (2001) 20(1) 65-75; Prasad et al., AlkaliTreatment Of Coir-Polyester Composites, J. of Materials Science (1983)18(5), 1443-54; Rout et al., Novel Eco-Friendly BiodegradableCoir-Polyester Amide Biocomposites, Polymer Composites (2001) 22(6),770-78; Rahman et al., Surface Treatment Of Coir Fibers And ItsInfluence On The Fibers Physico-Mechanical Properties, CompositesScience and Tech. (2007) 67(11-12), 2369-76; Rozman et al., The EffectOf Lignin As A Compatibilizer On The Physical Properties Of CoconutFiber-Polypropylene Composites, Eur. Polym. J. (2000) 36(7), 1483-94;Hai et al., Advanced Composite Materials, (2009) 18(3), 197-208; Tan etal., Advanced Materials Research (2010) 139-141, 348-51; Carvalho etal., BioResources (2010) 5(2), 1143-55; Silva et al., Composites Scienceand Technology (2006) 66(10), 1328-35; Javadi et al., Processing AndCharacterization Of Solid And Microcellular PHBV/Coir fiber Composites,Materials Science and Eng. (2010) 30(5) 749-57; Rosa et al., BioresourceTechnology (2009) 100(21), 5196-5202; Geethamma et al., J. of AppliedPolymer Science (1995) 55(4), 583-94; Geethamma et al., Polymer (1998)39(6-7), 1483-91; Wei et al., Characterisation And Utilization OfNatural Coconut Fibres Composites, Materials and Design (2009) 30,2741-44.

Moreover, some studies have been reported on WG-based composites filledwith natural fibers, such as, for example, hemp, jute, and coconut fiber(see, e.g., Kunanopparat et al., Plasticized Wheat Gluten ReinforcementWith Natural Fibers: Effect Of Thermal Treatment On The Fiber/MatrixAdhesion, Composites: Part A (2008) 39, 777-85 and 1787-1792; Wretforset al., Effects Of Fiber Blending And Diamines On Wheat Gluten MaterialsReinforced With Hemp Fiber, J. of Materials Science (2010) 45(15),4196-4205; Wretfors et al., J. of Polymers and the Environment (2009)17(4), 259-66; Reddy et al., Biocomposites Developed UsingWater-Plasticized Wheat Gluten As Matrix And Jute Fibers AsReinforcement, Polymer Int'l (2011) 60(4), 711-16; Muensri et al.,Effect Of Lignin Removal On The Properties Of Coconut Coir Fiber/WheatGluten Biocomposite, Composites, Part A: Applied Science and Mfg. (2011)42A(2), 173-79).

Some studies have been reported on the preparation of particleboardbased on coconut materials. For example, high density particleboardsfrom whole coconut husk have been produced without the addition ofchemical binders (see, e.g., Van Dam et al., Ind. Crops Prod. 2004,19(3), 207-216; Van Dam et al., Ind. Crops Prod. 2004, 20(1), 97-101;and Van Dam et al., Ind. Crops Prod. 2006, 24(2), 96-104). Moreover, CCPhas been used for manufacturing particleboards using UF and PF asbinders (see, e.g., Sampathrajan et al., Bioresour. Technol. 1992,40(3), 249-251; Viswanathan et al., Bioresour. Technol. 1998, 67(1),93-95; and Viswanathan et al., Bioresour. Technol. 2000, 71(1), 93-94).Additionally, insulating particleboards made from CCF with UF, PF andisocyanate binders have been reported (see, e.g., Khedari et al., Build.Envi. 2003, 38(3), 435-441). As noted above, there have also been somestudies reporting on using modified WG as a binder for woodparticleboards and fiberboards.

Thus, an interest exists for improved systems and methods for theproduction or fabrication of particleboard using non-formaldehyde-basedbinders. Stated another way, an interest exists for the design ofimproved formaldehyde-free particleboards. Moreover, a need remains forsystems/designs for the fabrication of particleboards (e.g.,formaldehyde-free particleboards) utilizing natural fibers/materials(e.g., lignocellulosic materials, such as coconut fibers and/ormaterials), wherein the particleboards have improved performancecharacteristics (e.g., mechanical properties) compared to conventionalparticleboards.

These and other inefficiencies and opportunities for improvement areaddressed and/or overcome by the systems, assemblies and methods of thepresent disclosure.

SUMMARY

The present disclosure provides advantageous particleboard and methodsfor fabricating advantageous particleboard (e.g., naturalfiber/material-based particleboard). In exemplary embodiments, thepresent disclosure provides for improved systems and methods forfabricating particleboard (e.g., formaldehyde-free particleboard)utilizing natural fibers/materials (e.g., lignocellulosic materials),wherein the particleboard has improved performance characteristicsand/or mechanical properties.

In general, the present disclosure provides for improved systems andmethods for fabricating a formaldehyde-free particleboard from fibersand/or lignocellulosic materials (e.g., coconut materials, such ascoconut coir pith and/or coconut fiber), along with a binder material(e.g., wheat gluten, diphenylmethane diisocyanate, polyurethane binderbased on palm oil polyol, etc.). In exemplary embodiments, the fiber orlignocellulosic material (e.g., coconut fiber) is treated with sodiumhydroxide and/or a silane coupling agent as an adhesion promoter toenhance interfacial adhesion between the fiber and the coir pith, and/orbetween the fiber/coir pith and the binder. The mechanical and physicalproperties of the disclosed eco-particleboards have been examined andcompared to, inter alia, the properties of a particleboard usingcommercial RUBINATE® binder (e.g., a water-compatible polyisocyanatebased on diphenylmethane diisocyanate).

In general, fiber-reinforced biocomposites (e.g., coconutfiber-reinforced wheat gluten (WG) biocomposites) may be advantageouslyfabricated. For example, natural fibers (e.g., coconut fibers) may bechemically modified by sodium hydroxide and/or a silane treatment. Inexemplary embodiments, (3-triethoxysilylpropyl)-t-butylcarbamate (MISO),which is a masked isocyanate functional silane, was advantageouslyutilized to improve interfacial adhesion between WG and the naturalfibers. Moreover, X-ray photoelectron spectroscopy (XPS) and gaschromatography/mass spectroscopy (GC/MS) were employed to prove thepresence of the silane on silane-treated coconut fiber (SCCF), and alsoto prove the presence of the silane on alkali-followed by silane-treatedfiber (ASCCF). In exemplary embodiments, it has been found that ASCCFhad more silane content on the fiber surface than SCCF. The mechanicalproperties of composites with about 15 mass % fiber loading have beenassessed by three-point bending tests. Moreover, scanning electronmicroscopy (SEM) was used to investigate fiber pullout characteristicsof composites. The WG/ASCCF composite provided about an 80% increase instrength, and showed superior fiber-matrix interfacial adhesion.

As noted, one exemplary silane utilized for the fiber treatment (e.g.,fiber surface treatment) was (3-triethoxysilylpropyl)-t-butylcarbamate,which is a masked isocyanate functional silane (MISO), with demaskingtemperatures about 150 to about 200° C. In exemplary embodiments, theeffects of surface treatments of the fibers with respect to mechanicalproperties of the biocomposites reinforced with the treated fibers havebeen investigated, as discussed further below.

The present disclosure provides for a method for fabricating aparticleboard including a) soaking a portion of a lignocellulosicmaterial in an alkali solution; b) drying the lignocellulosic materialafter soaking; c) soaking a portion of the lignocellulosic material in amasked isocyanate functional silane solution; d) drying thelignocellulosic material after soaking; and e) molding thelignocellulosic material.

The present disclosure also provides for a method for fabricating aparticleboard wherein at least a portion of the lignocellulosic materialis derived from natural fibers. The present disclosure also provides fora method for fabricating a particleboard wherein prior to step a), thelignocellulosic material is dried to a moisture content of from about 3%to about 4.5%.

The present disclosure also provides for a method for fabricating aparticleboard wherein step a) is performed by soaking thelignocellulosic material in about a 5% w/v alkali solution for about 4hours at about room temperature. The present disclosure also providesfor a method for fabricating a particleboard wherein the silane solutionincludes (3-triethoxysilylpropyl)-t-butylcarbamate. The presentdisclosure also provides for a method for fabricating a particleboardwherein the silane solution is prepared by dissolving(3-triethoxysilylpropyl)-t-butylcarbamate in about a 50/50 v/v solutionof water and acetone to form about 0.1 volume percent silane in thesolution.

The present disclosure also provides for a method for fabricating aparticleboard wherein step e) is performed by hot-press molding orcompression molding the lignocellulosic material. The present disclosurealso provides for a method for fabricating a particleboard wherein stepe) is performed by compression molding the lignocellulosic material atfrom about 150° C. to about 160° C. for about 7 to 20 minutes at fromabout 900 lb_(f) to about 40,000 lb_(f).

The present disclosure also provides for a method for fabricating aparticleboard wherein a binder material is added to the lignocellulosicmaterial after step d) and prior to step e). The present disclosure alsoprovides for a method for fabricating a particleboard wherein the bindermaterial is selected from the group consisting of wheat gluten,diphenylmethane diisocyanate, and polyurethane.

The present disclosure also provides for a method for fabricating aparticleboard wherein a coconut coir pith material is added to thelignocellulosic material after step d) and prior to step e). The presentdisclosure also provides for a method for fabricating a particleboardincluding: a) soaking a lignocellulosic material in a masked isocyanatefunctional silane solution; b) drying the lignocellulosic material aftersoaking; and c) molding the lignocellulosic material. The presentdisclosure also provides for a method for fabricating a particleboardwherein at least a portion of the lignocellulosic material is derivedfrom natural fibers.

The present disclosure also provides for a method for fabricating aparticleboard wherein prior to step a), the lignocellulosic material isdried to a moisture content of from about 3% to about 4.5%. The presentdisclosure also provides for a method for fabricating a particleboardwherein the silane solution is prepared by dissolving(3-triethoxysilylpropyl)-t-butylcarbamate in about a 50/50 v/v solutionof water and acetone.

The present disclosure also provides for a method for fabricating aparticleboard wherein the silane solution includes(3-triethoxysilylpropyl)-t-butylcarbamate. The present disclosure alsoprovides for a method for fabricating a particleboard wherein step c) isperformed by hot-press molding or compression molding thelignocellulosic material.

The present disclosure also provides for a method for fabricating aparticleboard wherein a binder material is added to the lignocellulosicmaterial after step b) and prior to step c).

The present disclosure also provides for a method for fabricating aparticleboard wherein the binder material is selected from the groupconsisting of wheat gluten, diphenylmethane diisocyanate, andpolyurethane. The present disclosure also provides for a method forfabricating a particleboard wherein a coconut coir pith material isadded to the lignocellulosic material after step b) and prior to stepc).

The present disclosure also provides for a method for fabricating aparticleboard including: a) contacting a portion of a lignocellulosicmaterial with a masked isocyanate functional silane; and b) molding thelignocellulosic material.

The present disclosure also provides for a method for fabricating aparticleboard wherein at least a portion of the lignocellulosic materialis derived from natural fibers.

The present disclosure also provides for a method for fabricating aparticleboard wherein the masked isocyanate functional silane includes(3-triethoxysilylpropyl)-t-butylcarbamate. The present disclosure alsoprovides for a method for fabricating a particleboard wherein before,during or after step a), a binder material is added to thelignocellulosic material prior to step b).

The present disclosure also provides for a method for fabricating aparticleboard wherein the masked isocyanate functional silane iscontacted with the portion of the lignocellulosic material via liquidspraying. The present disclosure also provides for a method forfabricating a particleboard wherein step a) includes mixing or blendingthe masked isocyanate functional silane with the portion of thelignocellulosic material.

The present disclosure also provides for a method for fabricating aparticleboard wherein at least a portion of the masked isocyanatefunctional silane is in powder or substantially solid form. The presentdisclosure also provides for a method for fabricating a particleboardwherein prior to step a) at least a portion of the lignocellulosicmaterial is soaked in an alkali solution.

The present disclosure also provides for a method for fabricating aparticleboard wherein step a) further includes mixing or blending abinder material with the portion of the lignocellulosic material.

Additional advantageous features, functions and applications of thedisclosed systems, assemblies and methods of the present disclosure willbe apparent from the description which follows, particularly when readin conjunction with the appended figures. All references listed in thisdisclosure are hereby incorporated by reference in their entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present disclosure are further describedwith reference to the appended figures. It is to be noted that thevarious steps, features and combinations of steps/features describedbelow and illustrated in the figures can be arranged and organizeddifferently to result in embodiments which are still within the spiritand scope of the present disclosure. To assist those of ordinary skillin the art in making and using the disclosed systems, assemblies andmethods, reference is made to the appended figures, wherein:

FIG. 1 depicts FTIR spectra of coconut fiber (CCF), and alkali-treatedfiber (ACCF) treated with 5 wt % NaOH solution;

FIGS. 2A-D depict FE-SEM micrographs (300X) of: (a) untreated coconutfiber (CCF), (b) alkali-treated coconut fiber (ACCF) in about 2.5 wt %NaOH solution, (c) alkali-treated coconut fiber (ACCF) in about 5 wt %NaOH solution, and (d) alkali-treated coconut fiber (ACCF) in about 10wt % NaOH solution;

FIG. 3 depicts XPS survey spectra of ACCF, and alkali-followed bysilane-treated fiber (ASCCF);

FIGS. 4A-D depict XPS high-resolution spectra of Si_(2p) at 102 eV andSi_(2s) at 154 eV in the region between 80 and 170 eV for: (a) ASCCF,(b) ACCF treated with about 5 wt % NaOH solution, (c) silane-treatedcoconut fiber (SCCF), and (d) CCF;

FIGS. 5A-C depict representative GC/MS analysis of masked isocyanatefunctional silane (MISO): FIG. 5A—gas chromatogram of MISO at aconcentration of about 4.95 ppb; FIG. 5B—mass spectrum of the GC peak atretention time of about 3.93 min; and FIG. 5C—mass spectrum oftert-butyl alcohol standard;

FIGS. 6A-C depict gas chromatograms of: (a) ACCF, (b) SCCF, and (c)ASCCF;

FIGS. 7A-E depict stress-strain curves of: (a) wheat gluten (WG)composites, (b) WG/15 wt % CCF composites, (c) WG/15 wt % SCCFcomposites, (d) WG/15 wt % ACCF (5% NaOH treatment) composites, and (e)WG/15 wt % ASCCF (5% NaOH treatment) composites;

FIGS. 8A-I depict images showing fiber pullout characteristics of: (a)WG/CCF composites, (b) WG/ACCF composites, and (c) WG/ASCCF compositesafter failure under tensile test, and SEM images of tensile fracturedsurface of (d, g) WG/CCF composites, (e, h) WG/ACCF composites, and (f,i) WG/ASCCF composites;

FIGS. 9A-D depict stress-strain curves of: a) coconut coir pith (CCP)particleboard, b) CCP/WG (90/10) particleboard, c) CCP/ASCCF (90/10)particleboard, and d) CCP/ASCCF/WG (80/10/10) particleboard;

FIGS. 10A-C depict particleboard images after the nail-driving test;

FIGS. 11A-H depict stress-strain curves of: a) CCP, b) CCP/ASCCF(90/10), c) CCP/WG (90/10), d) CCP/ASCCF/WG (80/10/10), e) CCP/RN(90/10), f) CCP/ASCCF/RN (80/10/10), g) CCP/PU (90/10), and h)CCP/ASCCF/RU (80/10/10) small bar composites compressed at 160° C. with8.9×10⁷ N/m² (molding condition #2);

FIG. 12A depicts MOE, and FIG. 12B depicts MOR, for the followingfabricated particleboards: (i) CCP, (ii) CCP/ASCCF/WG, (iii)CCP/ASCCF/RN, and (iv) CCP/ASCCF/PU, compared with the minimumrequirement of MOE and MOR for the M-1 particleboard according to theANSI A208.1;

FIGS. 13A-H depict particleboard images after the nail-driving test;

FIG. 14 depicts thermo-gravimetric analysis of exemplary particleboardsof Example 4; and

FIG. 15 depicts a stress-strain curve for an exemplary bagasse-basedparticleboard fabricated according to the present disclosure.

DETAILED DESCRIPTION

The present disclosure provides for improved particleboard and methodsfor fabricating improved particleboard (e.g., naturalfiber/material-based particleboard). More particularly, the presentdisclosure provides for systems and methods for fabricatingparticleboard (e.g., formaldehyde-free particleboard) utilizing naturalfibers/materials (e.g., lignocellulosic materials), wherein theparticleboard has improved performance characteristics and/or mechanicalproperties.

In general, the present disclosure provides for systems and methods forfabricating fiber-reinforced biocomposites (e.g., naturalfiber-reinforced wheat gluten (WG) biocomposites). For example, thepresent disclosure provides systems/methods for fabricatingparticleboard (e.g., formaldehyde-free particleboard) fromlignocellulosic materials (e.g., coconut coir pith and/or coconutfiber), along with a binder material (e.g., wheat gluten, methyldiisocyante, a polyurethane binder, etc.).

In general, the fiber or lignocellulosic material (e.g., coconutfiber/coir pith) is treated with sodium hydroxide and/or a silanecoupling agent as an adhesion promoter to enhance interfacial adhesionbetween the fiber and the coir pith, and/or between the fiber/materialand the binder. In certain embodiments, the present disclosure providesa process for producing particleboard from coconut coir pith wherecoconut fiber is used as a reinforcement, and wheat gluten and/or methyldiisocyante is used as a binder.

In exemplary embodiments, (3-triethoxysilylpropyl)-t-butylcarbamate(MISO), which is a masked isocyanate functional silane, may beadvantageously utilized to improve interfacial adhesion between thebinder (e.g., WG) and the natural fibers/materials (e.g., CCF). MISO isa masked isocyanate functional silane, with demasking temperatures about150 to about 200° C. In exemplary embodiments, the composite (e.g.,WG/ASCCF composite) provided about an 80% increase in strength, andshowed superior fiber-matrix interfacial adhesion.

Current practice provides that urea-formaldehyde (UF) andphenol-formaldehyde (PF) resins are typical binders used by theparticleboard industry. However, UF and PF resins are generally neithereco-friendly nor safe due to health effects of exposure to formaldehydeemissions. Moreover, formaldehyde-based adhesives are derived fromgenerally unsustainable petrochemicals. Furthermore, some advantages ofnatural fibers over traditional reinforcing and man-made fibers aretheir low cost, low density, good specific mechanical properties, hightoughness, non-abrasive behavior during processing, enhanced energyrecovery, biodegradability and availability. In exemplary embodiments,the present disclosure provides systems/methods for fabricatingparticleboard (e.g., formaldehyde-free particleboard) utilizing naturalfibers/materials (e.g., lignocellulosic materials), wherein theparticleboard has improved performance characteristics and/or mechanicalproperties, thereby providing a significant manufacturing, commercialand environmental advantage as a result.

As noted, the present disclosure provides for improved systems/methodsfor fabricating a formaldehyde-free particleboard from fibers and/orlignocellulosic materials, along with a binder material (e.g., wheatgluten, diphenylmethane diisocyanate, etc.). In exemplary embodiments,the fiber/lignocellulosic material is treated with sodium hydroxideand/or a silane coupling agent as an adhesion promoter to enhanceinterfacial adhesion between the fiber and the binder.

As such, the present disclosure provides that fiber-reinforcedbiocomposites may be advantageously fabricated. For example, naturalfibers may be chemically modified by sodium hydroxide and/or a silanetreatment. In exemplary embodiments,(3-triethoxysilylpropyl)-t-butylcarbamate (MISO), which is a maskedisocyanate functional silane, may be advantageously utilized to improveinterfacial adhesion between the binder (e.g., wheat gluten) and thenatural fibers. Moreover, X-ray photoelectron spectroscopy (XPS) and gaschromatography/mass spectroscopy (GC/MS) have been employed to prove thepresence of the silane on silane-treated fiber, and also to prove thepresence of the silane on alkali-followed by silane-treated fiber.

As noted, one exemplary silane utilized for the fiber treatment (e.g.,fiber surface treatment) was (3-triethoxysilylpropyl)-t-butylcarbamate,which is a masked isocyanate functional silane (MISO), with demaskingtemperatures about 150 to about 200° C. In exemplary embodiments, theeffects of surface treatments of the fibers with respect to mechanicalproperties of the biocomposites reinforced with the treated fibers havebeen investigated, as discussed below.

The present disclosure will be further described with respect to thefollowing examples; however, the scope of the disclosure is not limitedthereby. The following examples illustrate the process of the disclosureof producing particleboard (e.g., formaldehyde-free particleboard)utilizing natural fibers/materials (e.g., lignocellulosic materials),wherein the particleboard has improved performance characteristicsand/or mechanical properties.

Example 1

Materials: The American vital wheat gluten (WG) was supplied byArrowhead Mills, USA, and contained about 80% proteins, about 10% waterand about 10% starch, along with other minor components such as lipidsand ash (see, e.g., Ye et al., J. Polym Environ., 2006, 14, 1-7).

The wheat gluten was dried in a vacuum oven at about 50° C. for about 12hours (moisture content about 3%) before use.(3-triethoxysilylpropyl)-t-butylcarbamate (masked isocyanate silane;MISO) was purchased from Gelest Inc., USA. Sodium hydroxide was suppliedby Fisher Scientific, USA. Acetone was obtained from J.T. Baker, USA.The coconut fiber (CCF) was received from Lanka Coco Products, Ltd., SriLanka. Physical and mechanical properties of coconut fiber are shown inTable 1.

It is noted that other fibers or lignocellulosic fibers/materials (e.g.,tree fibers/materials, bamboo, hemp, cereal straw, rice husks, bagasse,etc.) may be used in lieu of CCF in the systems, processes, methods andexamples of the present disclosure. In this regard, it is noted thatlignocellulosic fiber chemistry indicates that the masked isocyanatesilane chemistry applies to fibers from trees (e.g., hardwood andsoftwood trees, such as, for example, pine, rubber, banana, etc.), aswell as to other plant fibers (e.g., bamboo, hemp, cereal straw, ricehusks, bagasse, etc.). It is further noted that lignocellulosicfibers/materials have many hydroxyl (OH) groups, and the maskedisocyanate silane deposition chemistry relies in part on silanolcondensation with the surface hydroxyls. Therefore, it is noted that theadvantageous masked isocyanate formulations of the present disclosureare effective with lignocellulosic fibers/materials.

TABLE 1 Physical and mechanical properties of coconut fiber and E-glassfiber (Kalia et al., Polym. Eng. Sci (2009) 49, 1253-72) Tensile Young'sElongation Density Diameter strength modulus at break Fiber (g/cm³) (μm)(MPa) (GPa) (%) Coconut fiber 1.15 100-450 131-175 4-6 15-40 E-glassfiber 2.5 — 2000-3500 70 2.5

It is noted that coconut fiber was not expected to add the very largeincreases in strength and stiffness obtained from glass fiberreinforcement, but the large elongation to break greatly improved theductility of the composites, as illustrated below.

Fiber Treatments:

Coconut fiber (CCF) with a diameter of about 0.30 to about 0.55 mm wascut into about 40 mm lengths, and was dried in a vacuum oven at about50° C. for about 2 hours (moisture content about 3%). Some of the CCFwas then subjected to fiber treatments (e.g., surface treatments), asdescribed below.

Alkali Treatment (Mercerization):

Some of the dried fibers (about 20 g) were soaked in about 2.5% w/vsodium hydroxide solution in water (about 1000 ml) for about 4 hours atroom temperature, then washed thoroughly with distilled water until therinse solution reached a pH of about 7.

Moreover, some of the dried fibers (about 20 g) were soaked in about 5%w/v sodium hydroxide solution in water (about 1000 ml) for about 4 hoursat room temperature, then washed thoroughly with distilled water untilthe rinse solution reached a pH of about 7.

Additionally, some of the dried fibers (about 20 g) were soaked in about10% w/v sodium hydroxide solution in water (about 1000 ml) for about 4hours at room temperature, then washed thoroughly with distilled wateruntil the rinse solution reached a pH of about 7.

Each batch (2.5% NaOH, 5% NaOH and 10% NaOH) of the alkali-treated fiber(ACCF) was dried at room temperature for about 12 hours, and then driedin a vacuum oven at about 50° C. for about 2 hours (moisture contentabout 3%).

Silane Treatment:

(3-triethoxysilylpropyl)-t-butylcarbamate (e.g., a masked isocyanatefunctional silane or MISO) was dissolved in about a 50/50 v/v solutionof water and acetone (about 0.1 volume % silane in the solution). The pHwas adjusted to about 4 with acetic acid, stirring the solutioncontinuously for about 30 minutes.

Some of the dried (non-alkali treated) coconut fibers, as well as someof the dried alkali-treated fibers (ACCF—2.5%, 5%, and 10% NaOHtreatment), were then soaked in the solution for about 2 hours.

The fibers were then removed from the silane solution, and the solventwas allowed to evaporate in an air stream at room temperature for about2 hours. The fibers were dried in a vacuum oven at about 50° C. forabout 12 hours. The CCF treated with only silane (non-alkali treated) isreferred to as SCCF, while the alkali-treated fiber which was alsotreated with silane is referred to as ASCCF.

It is noted that the present disclosure contemplates that the silane(e.g., masked isocyanate functional silane) may beincorporated/contacted and/or mixed/blended with the fibers, materials,mixtures, blends and/or samples in a variety of ways, and at variousdifferent steps in the fabrication process. For example, the silane(MISO) may be incorporated into the sodium hydroxide solution discussedabove, and the fibers may be simultaneously soaked in the NaOH and thesilane solution, followed by the drying and composite preparation (e.g.,mixing/incorporating with binder and/or molding) steps.

Alternatively, the silane (MISO) may be deposited (e.g., via liquidspraying or the like) onto the lignocellulosic fibers/materials (e.g.,after the NaOH treatment), and then the silane-treated fibers may bemixed/incorporated with a binder (if desired) and thenmolded/fabricated. It is noted that the lignocellulosic fibers/materialsmay be mixed/blended with the binder material (if desired) before,during, or after the silane treatment (e.g., silane treatment via liquidspraying or the like). For example, it is noted that the binder materialmay be contacted/deposited (e.g., via liquid spraying or the like) ontoand/or mixed/blended (e.g., as a liquid or solid) with thelignocellulosic fibers/materials before, during or after the silanetreatment (e.g., silane liquid spraying treatment, substantiallysolid-silane mixing step, and/or after silane solution soakingtreatment, etc.).

In certain embodiments, the alkali-treatment step (if desired) may befollowed by a silane-treatment step where the MISO silane ismixed/contacted with the other components (e.g., fibers/materials andbinder) in substantially one step (e.g., a solids mixing step withMISO/MISO powder and/or binder, and/or a liquid spray treatment stepwith MISO and/or binder, etc.), followed then by a molding/fabricationstep. As noted, the silane-treatment step(s) could have severalvariations, such as, for example, a silane-treatment step where thecomponents (fibers/materials, MISO silane and/or binder) aremixed/blended together as solids, and/or as a step where the MISO silaneand/or binder (if desired) is sprayed onto the lignocellulosicfibers/materials (and other solids) as a liquid.

Composite Preparation:

Mixtures (e.g., mixtures obtained via mechanical mixing or the like),blends or samples (about 700 mg total for each sample/mixture) of: (i)wheat gluten (WG); (ii) WG/CCF; (iii) WG/ACCF; (iv) WG/SCCF; and (v)WG/ASCCF were then compression-molded at about 150° C. for about 10minutes, and at about 8.9×10⁴N (about 20,000 lb_(f)), in a stainlesssteel mold to form about 4×0.5×0.2 cm bars.

For the mixtures, blends or samples that were fabricated into thecomposites/bars (ii) through (v) listed above, the ratio of WG to CCF,ACCF, SCCF or ASCCF was about 85/15 by weight percent.

Methods—Fourier Transform Infrared (FTIR) Spectroscopy:

FTIR spectra of ground CCF and ACCF were taken using a Nicolet Magna-IR560 spectrometer. The KBr pellet technique was used to prepare samples.Data was collected from 4000-400 cm⁻¹ in the middle-infrared region with32 scans at a resolution of about 4 cm⁻¹. The spectra were analyzedusing Omnic software, version 7.2a, from the Thermo ElectronCorporation.

Scanning Electron Microscopy (SEM):

The surface morphology of CCF and ACCF at various concentrations ofsodium hydroxide solution, as well as the fracture surfaces of allcomposites after failure under tensile test were examined by SEM usingJEOL 6335F field emission scanning electron microscope (FE-SEM) with 10kV accelerating voltage. All samples were coated with gold before SEMobservation.

X-Ray Photoelectron Spectroscopy (XPS) Surface Analysis:

The XPS spectra of CCF, SCCF, ACCF and ASCCF were recorded with aPerkin-Elmer PHI 595 Multiprobe system with an alumina/magnesium twinx-ray source. The fibers were mounted onto a holder with double-sidedcarbon tape and placed in a vacuum at about 10⁻⁸ torr. All the scanswere performed with a survey run of binding energy between 1100 to 0 eV,pass energy of 50 eV and ev/s=0.1 eV.

Gas Chromatography/Mass Spectroscopy (GC/MS) Analysis:

GC/MS determinations of ACCF, SCCF and ASCCF (about 1.1 g) wereperformed on a HP 6890 Series GC/MS system with direct dynamic thermaldesorption (syringeless injection). A Zebron ZB-1 capillary column (30mL×0.25 mm I.D.×1.00 μm film thickness) was used with temperatureprogram from 35 (held for about 2 min) to 325° C. using helium carriergas at about 15° C./min. The temperature of the splitless injector waskept at about 225° C. with purge delay time of about 2 min. Mass spectraof all samples were recorded at scan range of 10 to 700 dalton (scanrange 100 to 300 dalton at first 6 min).

Mechanical Property Testing:

The molded bars were used for a three-point bending test performedaccording to the standard test methods for flexural properties, ASTMD790-02. The tests were conducted on a computer-interfaced Instron 1011with a 50 N load cell. The rate of crosshead motion was about 1 mm/min,while the data acquisition rate was 10 points per second. Three to fivereplicates were performed for each sample.

Fracture Characteristic of WG Composites:

The molded bars prepared as described in the composite preparationsection were broken under tensile loading using the Instron 1011 withcross head speed of about 1 mm/min. The tensile fractured surface of thecomposites was observed by using JEOL 6335F FE-SEM. All fracturedspecimens were sputtered with gold prior to SEM examination.

Results and Discussion

Infrared Spectroscopy (FTIR):

FIG. 1 (a-b) shows FTIR spectra of CCF and ACCF treated with about 5 wt% NaOH solution, respectively. The change in surface composition of ACCFcan be investigated by infrared spectra. It can be seen that there is anabsorption band of the carbonyl groups in the hemicellulose at 1742 cm⁻¹in the CCF spectra (see, e.g., Mohanty et al., Natural Fibers,Biopolymers And Biocomposites, CRC Press, Taylor & Francis Group (2005)p. 199). However, no peak at 1742 cm⁻¹ is observed in the ACCF spectra.This change in the spectra indicates extraction of hemicellulose fromthe fiber surface by the aqueous alkaline solution during the surfacetreatment process.

SEM of Alkali-Treated Coconut Fiber (ACCF):

The morphology of untreated CCF and alkali-treated fibers (ACCF) atdifferent concentrations of sodium hydroxide solution investigated bySEM is shown in FIG. 2A-D. The alkali-treated CCF (FIGS. 2B-D) has arough surface topography and a fibrillar formation due to the removal ofimpurities, wax, as well as some hemicellulose and lignin covering theexternal surface of the fibers.

The surface of the untreated fiber (FIG. 2A) appears to be smoother thanthe alkali-treated fiber (see, e.g., Li et al., J. Polym. Environ.,(2007) 15, 25-33). In exemplary embodiments, the surface roughness mayenhance the fiber-polymer adhesion. Treatment with about 5% NaOHprovided better mechanical properties than the untreated CCF, the about2.5% NaOH ACCF, and the about 10% NaOH ACCF. Therefore, the exemplaryresults below for ACCF and ASCCF used the about 5% NaOH solution.

X-Ray Photoelectron Spectroscopy (XPS) Surface Analysis of all Fibers:

XPS analysis was used to give evidence of silane presence on the surfaceof SCCF and ASCCF. FIG. 3 presents the XPS survey spectra of electronintensity as a function of binding energy for ACCF and ASCCF. It isnoted that the survey spectra for CCF and SCCF look very similar (notshown). Elemental compositions on the surface of the fibers are alsosummarized in Table 2.

The peaks of carbon (C_(1s)) and oxygen (O_(1s)) at about 284 and 531eV, respectively, are predominant (see, e.g., Wagner et al., Handbook OfX-Ray Photoelectron Spectroscopy, Perkin-Elmer Corp., Eden Prairie,Minn., (1979)). The major elements including natural fibers, consistingof cellulose, hemicellulose, lignin and wax, are carbon, oxygen andhydrogen. Therefore, it is not surprising that high electron intensityof carbon and oxygen was detected in all cases. Elements such assilicon, potassium, sodium, magnesium, calcium, iron, aluminum, sulfur,copper, and phosphorus were also found in the coconut fibers in muchsmaller quantities (see, e.g., Raveendran et al., Fuel, (1995) 74,1812-22; histiz-Smith et al., Mater. Charact., (2008) 59, 1273-78).

In FIG. 3, a very small amount of silicon was observed near 102 and 154eV corresponding to Si_(2p) and Si_(2s), respectively, in ACCF (and alsoCCF). In the case of ASCCF (and SCCF), the intensity of Si_(2p) andSi_(2s) peaks at 102 and 154 eV is higher than that of ACCF. Inaddition, higher intensity of N_(1s) peak at 399 eV for ASCCF and SCCFwas detected compared to the coconut fibers without silane. Thehigh-resolution spectra of Si_(2p) and Si_(2s) in the region between 80and 170 eV, are presented in FIG. 4. Silane treatment more than doubledthe fraction of silicon on the surface of the fibers. Furthermore, therewas a significant increase in the amount of silicon present in spectraof ASCCF (FIG. 4A) compared to that of SCCF (FIG. 4C). Thus, thealkaline treatment of the fiber prior to silane increased the amount ofbonded silane on the surface of the fiber.

TABLE 2 Elemental surface compositions and binding energies for thefibers determined from XPS analysis. Elemental composition (%) C(1s)O(1s) Si(2p) N(1s) Fiber (284 eV) (531 eV) (102 eV) (399 eV) CCF 72.5924.33 1.94 1.14 ACCF 73.71 23.26 1.74 1.29 SCCF 69.81 23.11 4.53 2.55ASCCF 69.20 21.75 5.95 3.10

Gas Chromatography/Mass Spectroscopy (GC/MS) Analysis:

The masked isocyanate functional silane,(3-triethoxysilylpropyl)-t-butylcarbamate, or MISO, was used to improvethe adhesion of binder (e.g., wheat gluten) to fiber (e.g., coconutfiber). Because of its high reactivity, especially to moisture, and itstoxicity, isocyanate is generally vulnerable to premature reaction whenused with natural fibers.

In exemplary embodiments, isocyanate functionality of the MISO wasadvantageously masked in the form of carbamate. In general, demasking ofthe isocyanate group occurred during the heat-press processing step withdemasking temperatures around about 150 to about 200° C. (see, e.g.,Arkles, B., Silane Coupling Agents: Connecting Across Boundaries V2.0,Gelest, Inc., Morrisville, Pa., (2006) p. 16). During demasking of MISO(1), tert-butyl alcohol (2) was emitted and3-isocyanatopropyltriethoxysilane (3) was formed, as illustrated inScheme 1.

Gas chromatography/mass spectroscopy (GC/MS) was used to complement theXPS described above as an additional technique to check for the presenceof the silane on the fiber. As shown in Scheme 1, tert-butyl alcohol isreleased when MISO is heated, and at the demasking temperature, thetert-butyl alcohol is emitted as a vapor. GC/MS was employed to detectemitted tert-butyl alcohol from SCCF and ASCCF. The temperature of theGC injector was kept at about 225° C., which was a little bit higherthan the demasking temperature, to make sure that tert-butyl alcoholcompletely discharged from the silane-coated coconut fibers.

FIG. 5 demonstrates the ability of this technique to detect the emittedtert-butyl alcohol from the MISO demasking reaction. FIG. 5A presents agas chromatogram of a MISO reference at a concentration of about 4.95ppb. FIG. 5B shows the mass spectrum of the GC peak at retention time ofabout 3.93 min, corresponding to tert-butyl alcohol. A mass spectrum ofhigh purity tert-butyl alcohol, containing a prominent m/z 59 ion isprovided in FIG. 5C, illustrating very close correspondence with FIG. 5Band verifying that the GC peak at 3.93 min is indeed tert-butyl alcohol.Besides the tert-butyl alcohol found in the GC of demasked MISO,3-isocyanatopropyltriethoxysilane (3) was observed at a retention timeof about 12.74 min, and this was also verified with mass spectroscopy.

The gas chromatograms of ACCF, SCCF, and ASCCF, at retention timesbetween about 2.5 and about 5 min, are presented in FIGS. 6A-C. In FIG.6A, there is no appearance of tert-butyl alcohol peak at retention timeof about 3.93 min. On the other hand, the GC/MS analysis revealed thatSCCF and ASCCF contained a peak with a retention time at about 3.93 minconsistent with tert-butyl alcohol. Moreover, the peak area of m/z 59ion of tert-butyl alcohol in the chromatogram of ASCCF is higher thanthat of SCCF, as shown in Table 3, implying more of the silane bonded toASCCF than to SCCF. This result is in agreement with the result found inthe XPS analysis. It is noted that additional work with calibratedstandards is to be performed for quantitative analysis of the silanesurface coverage on coconut fibers.

TABLE 3 Peak area of m/z 59 ion of tert-butyl alcohol for SCCF andASCCF: Retention time of tert-butyl Peak area of m/z 59 ion of Samplealcohol (min) tert-butyl alcohol ACCF N/A 0 SCCF 3.926 1.5 × 10⁶ ASCCF3.928 6.6 × 10⁶

Mechanical Properties of Prepared Composites:

The mechanical properties of the exemplary composites are shown in Table4. The first failure stress values are the stresses at which the wheatgluten (WG) matrix began to crack, and are illustrated in FIGS. 7A-E.The mechanical properties of the WG composite with unmodified fiber(WG/CCF) slightly improved with respect to those of WG plastic (FIGS. 7Aand 7B).

With regards to alkaline treatment, the mechanical properties of WGcomposites with ACCF treated in low concentration (about 2.5% NaOHsolution) were comparable to those of the WG/CCF composite, whereas theproperties of WG/ACCF treated in about 10% NaOH solution decreased withrespect to the WG/CCF composite. Without being bound by any theory, itis believed that the decrease in strength may be due to the highalkaline concentration depolymerizing the native cellulose, resulting ina weaker or damaged fiber, which can adversely affect fiber strength.This result is consistent with the SEM result (FIG. 2D) showing thesurface topography of alkali-treated fiber. A similar trend of decreasein the strength of composites reinforced with natural fiber treated withabout 10 wt % NaOH solution has been reported (see, e.g., Mishra et al.,Compos. Sci. Technol., (2003) 63, 1377-85).

In exemplary embodiments of the present disclosure, the optimum NaOHconcentration found was about 5% NaOH. This concentration was used forthe ASCCF preparations. In general, without alkali surface treatment,the silane-treated fiber reinforced composite (WG/SCCF) provided littleimprovement in the mechanical properties compared to the WG/CCFcomposite. In exemplary embodiments, it was found that thealkali-followed by silane-treated fiber reinforced composite (WG/ASCCF)significantly improved the mechanical properties. Without being bound byany theory, it is believed that this may be due to the removal of waxes,hemicelluloses, and/or partial lignin on the fiber surface, whichthereby enhances the availability of sites for the cellulose-silaneinteractions. Indeed, more of the silane was found on ASCCF than onSCCF, as noted/illustrated above in the XPS and GC/MS analyses.

TABLE 4 Mechanical properties of WG composites reinforced with coconutfiber: % NaOH Modulus First Failure Elongation Sample Treatment (GPa)Stress (MPa) (%) WG 0 2.78 ± 0.20 46.22 ± 1.56 1.61 ± 0.05 WG/CCF 0 2.97± 0.22 48.35 ± 2.28 1.69 ± 0.06 (85/15 wt %) WG/SCCF 0 3.04 ± 0.15 49.98± 2.57 1.74 ± 0.16 (85/15 wt %) WG/ACCF 2.5 2.98 ± 0.05 47.89 ± 1.421.65 ± 0.03 (85/15 wt %) WG/ACCF 5 3.14 ± 0.20 51.74 ± 3.68 1.61 ± 0.10(85/15 wt %) WG/ACCF 10 2.85 ± 0.11 45.55 ± 1.42 1.60 ± 0.04 (85/15 wt%) WG/ASCCF 5 3.28 ± 0.15 58.60 ± 2.17 1.89 ± 0.10 (85/15 wt %)

FIGS. 7A-E present typical stress-strain curves of WG and WG compositesreinforced with untreated and treated CCF. In FIG. 7A, there issubstantially no ductile behavior in the stress-strain curve of the WGcomposite, which is different from those of the composites reinforcedwith the fibers. For the WG/fiber composites, the first failure wherethe WG matrix cracked is shown in FIGS. 7B-E (arrow sign) and reportedin Table 4. After the WG matrix failure, the stress still increasedbecause it was transferred to the interface and the fibers. When theinterface and the fibers broke, a decrease in stress was observed. Inorder to qualitatively compare the interfacial adhesion of the WG matrixand the fibers in the composites, the ratio of maximum stress to stressat the first failure was calculated and reported in Table 5. TheWG/ASCCF composites showed the highest value of the ratio, whichindicates that this composite has the strongest interfacial interactionbetween the WG matrix and ASCCF. This most likely resulted in thesuperior mechanical properties of the WG/ASCCF composite.

TABLE 5 Ratio of maximum stress to stress at the first failure ofWG/fiber composites: Maximum stress Maximum stress/stress at Sample(MPa) the first failure WG 46.22 ± 1.56 1.00 ± 0.00 WG/CCF 53.19 ± 1.321.10 ± 0.04 WG/SCCF 58.98 ± 4.14 1.18 ± 0.05 WG/ACCF 65.70 ± 8.16 1.27 ±0.05 WG/ASCCF 83.83 ± 8.76 1.43 ± 0.08

Tensile Fracture Behavior and Surface Fracture Characteristic of WGComposites:

FIGS. 8A-I illustrate the fiber pullout characteristics of WG/CCF,WG/ACCF, and WG/ASCCF composites after failure under tensile testing.FIGS. 8A-C show the pulled out fibers and FIGS. 8D-I show the tensilefractured surfaces of the composites. From FIG. 8A, long fiber lengthsof pullout are found in WG/CCF composite, while long and short fiberpullout lengths are observed in WG/ACCF (FIG. 8B). In the case ofWG/ASCCF, much shorter fiber pullout length is clearly evident.

The fractured surface images of the WG/CCF composite show extensivefiber pullout where many smooth holes remain after the fibers werepulled out (FIG. 8D), indicating extensive interfacial debonding betweenCCF and the WG matrix (FIG. 8G). Compared to WG/CCF, the WG/ACCFcomposite showed less fiber pullout and debonding (FIG. 8E and FIG. 8H).In the case of WG/ASCCF composite, even less fiber pullout is observed.Also, the WG matrix appears well adhered to the broken fibers due to theabsence of gaps between fibers and surrounding matrix (FIG. 8F and FIG.8I). These results indicate very poor interfacial bonding between fiberand matrix in the WG/CCF composite, and weak interfacial adhesion in theWG/ACCF composite. However, in the case of the WG/ASCCF composite,improved fiber-matrix interfacial adhesion was observed, therebyenhancing the mechanical properties.

CONCLUSIONS

For the WG composites reinforced with coconut fiber, the interfacialadhesion between the fibers and the WG affects the mechanical propertiesof the composites. Fiber surface treatment with a masked isocyanatesilane can enhance WG matrix/coconut fiber adhesion. Alkali treatmentslightly improved surface adhesion by removing impurities, thehemicelluose, and/or lignin covering the CCF surface, thereby producinga rough surface topography of the ACCF. Substantial improvements inmechanical properties were obtained by following the alkali surfacetreatment with the silane treatment on the fiber. XPS and GC/MSindicated that the alkali surface treatment led to a much larger silanesurface coverage than if no alkali treatment was applied to the fiber.

The failure of the wheat gluten changed from very brittle with no CCF tovery ductile with CCF, ACCF, SCCF, and ASCCF reinforcement. The improvedadhesion in the ASCCF reinforced WG matrix led to a roughly 25% increasein the stress at the first failure point on the stress/strain curve anda roughly 80% increase in the maximum stress. The improved adhesion alsoreduced the fiber pullout lengths observed on the failure surfaces oftensile test specimens.

Example 2 Materials

American vital wheat gluten (WG) was supplied by Arrowhead Mills, USA.It contained about 80% proteins, about 10% water and about 10% starch,and other minor components such as lipids and ash. WG was dried in avacuum oven at about 50° C. for about 12 hours (moisture content about3%) before use.

Coconut fiber (CCF) and coconut coir pith (CCP) were received from LankaCoco Products, Ltd., Sri Lanka.(3-triethoxysilylpropyl)-t-butylcarbamate (a masked isocyanate silane)was purchased from Gelest Inc., USA. Sodium hydroxide was supplied byFisher Scientific, USA. Acetone was obtained from J.T. Baker, USA.

Coconut Fiber and Coconut Pith Preparation:

Coconut fiber (CCF) with a diameter around 0.30-0.55 mm was cut intoabout 40 mm lengths and was dried in a vacuum oven at about 50° C. forabout 2 hours (moisture content about 3%). Some of the CCF was thensubjected to surface treatments.

Coconut pith (CCP) was sieved to obtain a particle size of <250 μm anddried in a vacuum oven at about 50° C. for about 2-4 hours (moisturecontent about 10%).

As discussed above, it is again noted that other fibers orlignocellulosic fibers/materials (e.g., tree fibers/materials, bamboo,hemp, cereal straw, rice husks, bagasse, etc.) may be used in lieu ofCCF and/or CCP in the systems, processes, methods and examples of thepresent disclosure.

Fiber Treatments:

Alkaline Treatment (Mercerization):

Samples of dried fibers (CCF) were soaked in: (i) about 2.5%; (ii) about5%; and (iii) about 10% w/v sodium hydroxide solution in water for about4 hours at room temperature, then washed thoroughly with distilled wateruntil the rinse solution reached a pH of about 7. Each batch ofalkaline-treated fibers (ACCF) was then dried at room temperature forabout 12 hours, and then dried in a vacuum oven at about 50° C. forabout 2 hours (moisture content about 3%).

Silane Treatment:

(3-triethoxysilylpropyl)-t-butylcarbamate of about 5 wt %, with respectto the fiber weight, was dissolved in about a 50/50 v/v solution ofwater and acetone (about 0.1 volume % silane in the solution). The pHwas adjusted to about 4 with acetic acid, stirring the solutioncontinuously for about 30 minutes.

Some of the dried (non-alkali treated) CCF, as well as some of the driedalkali-treated fibers (ACCF—2.5%, 5% and 10% NaOH treatment), were thensoaked in the silane solution for about 2 hours. The fibers were thenremoved from the solution, and the solvent was allowed to evaporate inan air stream at room temperature for about 2 hours. The fibers weredried in a vacuum oven at about 50° C. for about 12 hours. The CCFtreated with only silane (non-alkali treated) is referred to as SCCF,while the alkali-treated fiber which was also treated with silane isreferred to as ASCCF.

Again, it is noted that the present disclosure contemplates that thesilane (e.g., masked isocyanate functional silane) may beincorporated/contacted and/or mixed/blended with the fibers, materials,mixtures, blends and/or samples in a variety of ways, and at variousdifferent steps in the fabrication process. For example, the silane(MISO) may be incorporated into the sodium hydroxide solution discussedabove, and the fibers may be simultaneously soaked in the NaOH and thesilane solution, followed by the drying and composite preparation (e.g.,mixing/incorporating with binder and/or molding) steps.

Alternatively, the silane (MISO) may be deposited (e.g., via liquidspraying or the like) onto the lignocellulosic fibers/materials (e.g.,after the NaOH treatment), and then the silane-treated fibers may bemixed/incorporated with a binder (if desired) and thenmolded/fabricated. It is noted that the lignocellulosic fibers/materialsmay be mixed/blended with the binder material (if desired) before,during, or after the silane treatment (e.g., silane treatment via liquidspraying or the like). For example, it is noted that the binder materialmay be contacted/deposited (e.g., via liquid spraying or the like) ontoand/or mixed/blended (e.g., as a liquid or solid) with thelignocellulosic fibers/materials before, during or after the silanetreatment (e.g., silane liquid spraying treatment, substantiallysolid-silane mixing step, and/or after silane solution soakingtreatment, etc.).

In certain embodiments, the alkali-treatment step (if desired) may befollowed by a silane-treatment step where the MISO silane ismixed/contacted with the other components (e.g., fibers/materials andbinder) in substantially one step (e.g., a solids mixing step withMISO/MISO powder and/or binder, and/or a liquid spray treatment stepwith MISO and/or binder, etc.), followed then by a molding/fabricationstep. As noted, the silane-treatment step(s) could have severalvariations, such as, for example, a silane-treatment step where thecomponents (fibers/materials, MISO silane and/or binder) aremixed/blended together as solids, and/or as a step where the MISO silaneand/or binder (if desired) is sprayed onto the lignocellulosicfibers/materials (and other solids) as a liquid.

Composite Particleboard Preparation:

Small bars (about 4×0.5 cm) of the composites were prepared first toexamine the mechanical properties, while larger samples orparticleboards (about 14×21.5 cm) were prepared for nail-driving tests.Table 6 below lists the approximate weight percent ratios of the variouscomponents for the exemplary composites/particleboards.

The CCP, CCP/WG, CCP/ASCCF, and CCP/ASCCF/WG samples, mixtures (e.g.,mechanical mixtures) or blends (about 700 mg total sample/mixture weightfor each small bar, and about 105 g total sample/mixture weight for eachbig board) were compression-molded at about 160° C. for about 20 minutesat about 20 klb_(f) in a mold to form the small bars, and at about 160°C. for about 20 minutes at about 30-40 klb_(f) for the bigparticleboards.

Mechanical Property Testing:

The small molded bars were used for a three-point bending test performedaccording to ASTM D790-02, while the mechanical property tests of thebig particleboards were performed according to the standard test methodsfor evaluating properties for wood-based fiber and particle panelmaterials, ASTM D1037-99A.

Nail-Driving Test:

This test was made to examine the strength of the boards when nails weredriven into them. Nails of about 2.18 mm in diameter were driven intothe particleboards substantially perpendicular to the plane of theboards. Four replicates were performed for each sample. The results ofthe nail-driving test are shown in FIGS. 10A-C.

Results and Discussion:

The small bars of the coconut-based particleboards were prepared todetermine the mechanical properties of the boards as shown in Table 6.FIGS. 9A-D also show the stress-strain curves of the particleboards. Thecoconut pith particleboard made from coconut pith with the WG binder(CCP/WG) has higher modulus and strength than the particleboard withoutthe binder. In the case of the binderless particleboards, the CCP/ASCCFboard has better mechanical properties than the CCP board. In general,the CCP/ASCCF/WG particleboard has the most desirable properties. Theseresults indicate that wheat gluten is a good binder. The addition of theASCCF into the WG-glued particleboard enhances the mechanical propertiesof the composite particleboard.

TABLE 6 Mechanical properties of particleboards based on coconutmaterials: Ratio Modulus^(a)) Strength^(a)) Elongation^(a)) Composites(% wt) (GPa) (MPa) (%) CCP 100 2.97 ± 0.24 23.69 ± 3.05 0.81 ± 0.11CCP/WG 90/10 3.58 ± 0.18 30.08 ± 1.14 0.86 ± 0.07 CCP/ASCCF 90/10 3.44 ±0.15 30.97 ± 1.41^(b)) 0.96 ± 0.07^(b)) CCP/ASCCF/ 80/10/10 3.62 ± 0.2934.11 ± 1.97^(b)) 1.09 ± 0.09^(b)) WG ^(a))The mechanical propertieswere determined by a three-point bending test according to ASTM D790-02and the dimension of the specimen is about 4 × 0.5 × 0.2 cm. ^(b))Firstfailure point on stress-strain curves

In general, for indoor applications, particleboards are sometimes nailedfor installation, so it is desired to examine the strength of theparticleboards during nail driving. The results of the nail-driving testare shown in FIGS. 10A-C. It can be seen that when the nail is driveninto the boards, there is substantially no crack on the surface of theCCP/WG and CCP/ASCCF/WG particleboards, while the failure appears in theCCP board (FIG. 10A). As such, WG can bind either CCP or CCP/ASCCF toobtain tougher particleboards. In exemplary embodiments, the naildriving test was performed three times, with the substantially identicalresults illustrated in FIGS. 10A-C.

Conclusion Example 2

The composite particleboard from coconut pith with WG had more desirablemechanical properties than the particleboard without WG. It was alsofound that the addition of the silane-treated coconut fiber (ASCCF) intothe WG-bound particleboard enhances the mechanical properties. Thissuggests that WG can advantageously replace formaldehyde or the like asa particleboard binder.

Example 3

In certain embodiments, the present disclosure provides a process forproducing particleboard from coconut coir pith and where coconut fiberis used as a reinforcement, and either wheat gluten or methyldiisocyante is used as a binder. As discussed above, it is again notedthat other fibers or lignocellulosic fibers/materials (e.g., treefibers/materials, bamboo, hemp, cereal straw, rice husks, bagasse, etc.)may be used in lieu of CCF and/or CCP in the systems, processes, methodsand examples of the present disclosure.

In exemplary embodiments, the present disclosure relates to using maskedisocyanate silane, for example(3-triethoxysilylpropyl)-t-butylcarbamate, to treat natural fibers(e.g., coconut fibers) for producing composite particleboard fromlignocellulosic fibers/materials (e.g, coconut coir pith and/or CCF).The present disclosure also relates to using both alkali and the silanetreatment of the fiber (CCF). In an exemplary embodiment, the silaneused for the treatment is (3-triethoxysilylpropyl)-t-butylcarbamate.

In exemplary embodiments, the fibers were subjected to the alkalitreatment first and then by the silane treatment. The present disclosurefurther relates to the production of the coconut pith particleboard andthe coconut pith particleboard reinforced with surface treated coconutfibers.

In exemplary embodiments, the present disclosure provides wheat glutenmodified by thiolated additives, and particularly thiolated poly(vinylalcohol), as a binder for producing the particleboard. In general, thepresent disclosure provides several environmental advantages. Forexample, with exemplary formulations, an environmentally friendly binderis utilized (e.g., wheat gluten). Moreover, exemplary compositematerials produced according to the present disclosure have improvedmechanical properties compared with previous work with wheat gluten as abinder. Furthermore, using thiolated WG binders opens up the developmentof a whole new family of binders and formulations.

Materials:

American vital wheat gluten (WG) was supplied by Arrowhead Mills, USA.It contained about 80% proteins, about 10% water and about 10% starch,and other minor components such as lipids and ash. WG was dried in avacuum oven at about 50° C. for about 12 hours (moisture content about3%) before use. Coconut fiber (CCF) and coconut coir pith (CCP) werereceived from Lanka Coco Products, Ltd., Sri Lanka.(3-triethoxysilylpropyl)-t-butylcarbamate (masked isocyanate silane) waspurchased from Gelest Inc., USA. Sodium hydroxide was supplied by FisherScientific, USA. Acetone was obtained from J.T. Baker, USA.

Coconut Fiber and Coconut Pith Preparation:

Coconut fiber (CCF) with a diameter around 0.30-0.55 mm was cut intoabout 40 mm lengths and was dried in a vacuum oven at about 50° C. forabout 2 hours (moisture content about 3%). Some of the CCF was thensubjected to treatments (e.g., fiber surface treatments). Coconut pith(CCP) was sieved to obtain a particle size of <250 μm and dried in avacuum oven at about 50° C. for about 2-4 hours (moisture content about10%).

Fiber Treatments:

Alkaline Treatment (Mercerization):

Samples of dried fibers (CCF) were soaked in: (i) about 2.5%; (ii) about5%; and (iii) about 10% w/v sodium hydroxide solution in water for about4 hours at room temperature, then washed thoroughly with distilled wateruntil the rinse solution reached a pH of about 7. The samples of thealkaline-treated fibers (ACCF) were then dried at room temperature forabout 12 hours, and then dried in a vacuum oven at about 50° C. forabout 2 hours (moisture content about 3%).

Silane Treatment:

(3-triethoxysilylpropyl)-t-butylcarbamate of about 5 wt %, with respectto the fiber weight, was dissolved in about a 50/50 v/v solution ofwater and acetone (about 0.1 vol % silane in the solution). The pH wasadjusted to about 4 with acetic acid, stirring the solution continuouslyfor about 30 minutes.

Some of the dried (non-alkali treated) CCF, as well as some of the driedalkali-treated fibers (ACCF—2.5%, 5% and 10% NaOH treatment), were thensoaked in the silane solution for about 2 hours. The fibers were thenremoved from the solution, and the solvent was allowed to evaporate inan air stream at room temperature for about 2 hours. The fibers weredried in a vacuum oven at about 50° C. for about 12 hours. The CCFtreated with only silane (non-alkali treated) is referred to as SCCF,while the alkali-treated fiber which was also treated with silane isreferred to as ASCCF.

Again, it is noted that the present disclosure contemplates that thesilane (e.g., masked isocyanate functional silane) may beincorporated/contacted and/or mixed/blended with the fibers, materials,mixtures, blends and/or samples in a variety of ways, and at variousdifferent steps in the fabrication process. For example, the silane(MISO) may be incorporated into the sodium hydroxide solution discussedabove, and the fibers may be simultaneously soaked in the NaOH and thesilane solution, followed by the drying and composite preparation (e.g.,mixing/incorporating with binder and/or molding) steps.

Alternatively, the silane (MISO) may be deposited (e.g., via liquidspraying or the like) onto the lignocellulosic fibers/materials (e.g.,after the NaOH treatment), and then the silane-treated fibers may bemixed/incorporated with a binder (if desired) and thenmolded/fabricated. It is noted that the lignocellulosic fibers/materialsmay be mixed/blended with the binder material (if desired) before,during, or after the silane treatment (e.g., silane treatment via liquidspraying or the like). For example, it is noted that the binder materialmay be contacted/deposited (e.g., via liquid spraying or the like) ontoand/or mixed/blended (e.g., as a liquid or solid) with thelignocellulosic fibers/materials before, during or after the silanetreatment (e.g., silane liquid spraying treatment, substantiallysolid-silane mixing step, and/or after silane solution soakingtreatment, etc.).

In certain embodiments, the alkali-treatment step (if desired) may befollowed by a silane-treatment step where the MISO silane ismixed/contacted with the other components (e.g., fibers/materials andbinder) in substantially one step (e.g., a solids mixing step withMISO/MISO powder and/or binder, and/or a liquid spray treatment stepwith MISO and/or binder, etc.), followed then by a molding/fabricationstep. As noted, the silane-treatment step(s) could have severalvariations, such as, for example, a silane-treatment step where thecomponents (fibers/materials, MISO silane and/or binder) aremixed/blended together as solids, and/or as a step where the MISO silaneand/or binder (if desired) is sprayed onto the lignocellulosicfibers/materials (and other solids) as a liquid.

Composite Particleboard Preparation:

Sample bars (about 4×0.5×0.2 cm) of the composites were prepared toexamine the mechanical properties. The samples, mixtures (e.g.,mechanical mixtures) or blends were compression-molded at about 160° C.for about 20 minutes at about 20 klb_(f) in a mold to form the bars.Table 7 below lists the approximate weight percent ratios of the variouscomponents for the exemplary mixtures/bars/composites.

Mechanical Property Testing:

The molded bars were used for a three-point bending test performedaccording to ASTM D790-02.

Results and Discussion:

The bars of the coconut particleboards were prepared to determine themechanical properties as shown in Table 7.

TABLE 7 Mechanical properties of particleboards based on coconutmaterials: Ratio Modulus^(a)) Strength^(a)) Elongation^(a)) Composites(% wt) (GPa) (MPa) (%) Coconut Coir Pith (CCP) 100 3.83 ± 0.11 31.76 ±0.98 0.86 ± 0.03 CCP/Wheat Gluten (WG) 95/5 3.97 ± 0.16 35.51 ± 1.560.93 ± 0.05 CCP/WG 90/10 3.83 ± 0.10 40.57 ± 1.47 1.03 ± 0.07 CCP/Alkaliwashed and 90/10 4.38 ± 0.21 41.86 ± 1.61^(b)) 0.99 ± 0.07^(b)) silanetreated coconut fiber (ASCCF) CCP/ASCCF/WG 85/5/10 3.95 ± 0.16 41.13 ±1.61^(b)) 1.07 ± 0.06^(b)) CCP/ASCCF/WG 80/10/10 4.00 ± 0.14 45.60 ±1.58^(b)) 1.09 ± 0.10^(b)) CCP/Huntsman Rubinate 95/5 3.75 ± 0.11 43.44± 1.88 1.22 ± 0.14 methyl diisocyanate binder (RN) CCP/RN 90/10 3.59 ±0.12 46.28 ± 1.75 1.33 ± 0.06 CCP/ASCCF/RN 85/5/10 3.69 ± 0.10 47.87 ±2.07^(b)) 1.34 ± 0.04^(b)) CCP/ASCCF/RN 80/10/10 3.51 ± 0.09 50.78 ±1.86^(b)) 1.48 ± 0.08^(b)) ^(a))The mechanical properties weredetermined by a three-point bending test according to ASTM D790-02 andthe dimension of the specimen is 4 × 0.5 × 0.2 cm. ^(b))First failurepoint on stress-strain curves

Example 4

In exemplary embodiments, formaldehyde-free particleboard was preparedbased on coconut pith (CCP) with three different binders: wheat gluten(“WG”), commercial polyisocyanate (RUBINATE®1780, or “RN”), andcommercial polyurethane (“PU”).

As noted below, the mechanical and physical properties of theeco-particleboards have been examined. More particularly, the mechanicalproperties of the WG-bound particleboard is compared with those ofparticleboards using two commercial binders: RUBINATE®1780 (RN), whichis a water-compatible polyisocyanate based on diphenylmethanediisocyanate, and a polyurethane binder (PU) based on palm oil polyol.

As discussed further below, alkali-treated fiber, followed bysilane-treated coconut fiber (ASCCF) at about 10 wt % fiber was used toreinforce the particleboards. As discussed below, small bar samples wereprepared to determine results for mechanical properties (e.g.,evaluation by a three-point bending test). The effects of moldingpressure, binder type, and binder content on the mechanical propertieswere also investigated.

The modulus of elasticity (“MOE”), the modulus of rupture (“MOR”),tensile strength parallel to surface (“TS”), water absorption (“WA %”),thickness swelling (“TSW %”), and thermal stability of theparticleboards were also investigated. Additionally, the MOE and MOR ofthe boards were also compared with the minimum MOE and MOR requirementsfor commercial particleboard products as specified by the AmericanNational Standard Institute (ANSI), in ANSI A208.1-1999 forparticleboard.

Materials:

The coconut fiber (CCF) and coconut coir pith (CCP) were received fromLanka Coco Products, Ltd., Sri Lanka. The American vital wheat gluten(WG) was supplied by Arrowhead Mills, USA. It contained about 80%proteins, about 10% water and about 10% starch, along with other minorcomponents such as lipids and ash. The WG was dried in a vacuum oven atabout 50° C. for about 12 hours (moisture content about 3%) before use.

RUBINATE®1780 (“RN”), a methylene diphenyl diisocyanate binder, wassupplied by Huntsman Polyurethanes, USA. Polyurethane binder (“PU”) wasreceived from AURA P.U. TECH (M) SDN BHD, Malaysia. The PU binderincludes two parts: (i) AURATHANE@BR10, a palm oil-based polyol, and(ii) AURANATE@BH10, a polyisocyanate hardener for the palm oil-basedpolyol binder.

(3-triethoxysilylpropyl)-t-butylcarbamate (masked isocyanate silane orMISO) was purchased from Gelest Inc., USA. The sodium hydroxide wassupplied by Fisher Scientific, USA. Acetone was obtained from J.T.Baker, USA.

It is again noted that other fibers or lignocellulosic fibers/materialsmay be used in lieu of CCF and/or CCP in the systems, processes, methodsand examples of the present disclosure.

Coconut Fiber and Coconut Pith Preparation:

Coconut fiber (CCF) with a diameter in the range from about 0.30 mm toabout 0.55 mm was cut into about 40 mm lengths and was dried in a vacuumoven at about 50° C. for about 2 hours (moisture content about 3%). Someof the CCF was then subjected to surface treatments.

Coconut pith (CCP) was sieved to obtain a particle size of <250 μm anddried in a vacuum oven at about 50° C. for about 2-4 hours (moisturecontent about 10%) before preparing composite samples.

It is noted that for composites containing the PU binder, excessivemoisture content of the materials might affect the PU binderperformance. More particularly, the recommended moisture content ofmaterials used with the PU binder is less than about 5% moisturecontent. Thus, the CCP for use with the PU binder was dried in a vacuumoven at about 50° C. for about 8-10 hours to obtain a lower moisturecontent (e.g., moisture content less than about 5%).

Fiber Treatments:

Alkali Treatment (Mercerization):

Samples of dried fibers (CCF) were soaked in about 5% w/v sodiumhydroxide solution in water for about 4 hours at room temperature, thenwashed thoroughly with distilled water until the rinse solution reacheda pH of about 7. Each batch of alkaline-treated fibers was then dried atroom temperature for about 12 hours, and then dried in a vacuum oven atabout 50° C. for about 2 hours (moisture content about 3%).

Silane Treatment:

(3-triethoxysilylpropyl)-t-butylcarbamate of about 5 weight %, withrespect to the fiber weight, was dissolved in about a 50/50 v/v solutionof water and acetone (about 0.1 volume % silane in the solution). The pHwas adjusted to about 4 with acetic acid, stirring the solutioncontinuously for about 30 minutes.

Some of the dried alkali-treated (5% NaOH) coconut fibers were thensoaked in the silane solution for about 2 hours. The fibers were thenremoved from the solution, and the solvent was allowed to evaporate inan air stream at room temperature for about 2 hours. The fibers werethen dried in a vacuum oven at about 50° C. for about 12 hours. Thealkali-followed by silane-treated fiber is referred to as ASCCF. Some ofthe ASCCF was utilized to prepare composite samples, as discussedfurther below.

As discussed above in conjunction with Example 1, the interaction of thesilane treatment with the fiber surface was examined with X-RayPhotoelectron Spectroscopy (XPS) and Gas Chromatography/MassSpectroscopy (GC/MS) to verify the deposition of the silane on the fibersurface and the demasking reaction that converts the carbamate toisocyanate at the particleboard consolidation temperature.

Again, it is noted that the present disclosure contemplates that thesilane (e.g., masked isocyanate functional silane) may beincorporated/contacted and/or mixed/blended with the fibers, materials,mixtures, blends and/or samples in a variety of ways, and at variousdifferent steps in the fabrication process. For example, the silane(MISO) may be incorporated into the sodium hydroxide solution discussedabove, and the fibers may be simultaneously soaked in the NaOH and thesilane solution, followed by the drying and composite preparation (e.g.,mixing/incorporating with binder and/or molding) steps.

Alternatively, the silane (MISO) may be deposited (e.g., via liquidspraying or the like) onto the lignocellulosic fibers/materials (e.g.,after the NaOH treatment), and then the silane-treated fibers may bemixed/incorporated with a binder (if desired) and thenmolded/fabricated. It is noted that the lignocellulosic fibers/materialsmay be mixed/blended with the binder material (if desired) before,during, or after the silane treatment (e.g., silane treatment via liquidspraying or the like). For example, it is noted that the binder materialmay be contacted/deposited (e.g., via liquid spraying or the like) ontoand/or mixed/blended (e.g., as a liquid or solid) with thelignocellulosic fibers/materials before, during or after the silanetreatment (e.g., silane liquid spraying treatment, substantiallysolid-silane mixing step, and/or after silane solution soakingtreatment, etc.).

In certain embodiments, the alkali-treatment step (if desired) may befollowed by a silane-treatment step where the MISO silane ismixed/contacted with the other components (e.g., fibers/materials andbinder) in substantially one step (e.g., a solids mixing step withMISO/MISO powder and/or binder, and/or a liquid spray treatment stepwith MISO and/or binder, etc.), followed then by a molding/fabricationstep. As noted, the silane-treatment step(s) could have severalvariations, such as, for example, a silane-treatment step where thecomponents (fibers/materials, MISO silane and/or binder) aremixed/blended together as solids, and/or as a step where the MISO silaneand/or binder (if desired) is sprayed onto the lignocellulosicfibers/materials (and other solids) as a liquid.

Preparation of Composite Samples:

In exemplary embodiments, two different types/sizes of composite sampleswere prepared: (i) smaller bars (e.g., bars of about 4 cm×0.5 cm) and,(ii) larger boards (e.g., boards of about 21 cm×14 cm×0.4 cm).

For the small bars, the mixtures, blends, samples or composites of: (i)CCP, (ii) CCP/ASCCF, (iii) CCP/binder, and (iv) CCP/ASCCF/binder wereprepared to examine the mechanical properties. Theformulations/blends/mixtures used to prepare the small bars of theexemplary composites are presented in Table 8 below. As such, Table 8below lists the approximate weight percent ratios of the variouscomponents for the exemplary small bars/composites.

For the composites/bars containing/including the RN or PU binders,acetone was mixed with these binders to reduce their viscosity. Ingeneral, the ratio of the binder (RN or PU) to acetone for preparationof the binder solution was about 1:2 wt/vol. The binder solution and theCCP were then mechanically mixed for about 5 minutes. For thecomposites/bars containing/including the WG binder, the WG wasmechanically mixed with the CCP for about 5 minutes without addingacetone.

In exemplary embodiments, the amount of ASCCF in the coconut pithcomposites for the small bars and the larger boards was constant atabout 10 wt %, with respect to total weight of composites (Tables 8-10and 12). For the composites reinforced with ASCCF, the fibers weresubstantially unidirectionally aligned in each mold for the small bars,whereas the fibers (ASCCF) were placed into each mold in a randomlyoriented manner for the larger boards.

In order to prepare the small bars, each sample/mixture/blend (about 700mg total for each sample/mixture) of CCP, CCP/ASCCF, CCP/binder (e.g.,binder is WG, RN or PU), or CCP/ASCCF/binder was compression-molded toform a bar/composite (each bar about 4 cm×0.5 cm) in a multi-cavitystainless steel mold at about 160° C. at two different molding forces:(i) at about 4.0×10³ N (900 lb_(f)) and, (ii) at about 8.9×10⁴ N (20,000lb_(f)), corresponding to pressure of about 4.0×10⁶ N/m² and about8.9×10⁷ N/m², respectively.

Five bars were prepared/fabricated at each molding force for eachdifferent sample/mixture/blend of CCP, CCP/ASCCF, CCP/binder, orCCP/ASCCF/binder. The thickness of the bars after compression molding atabout 4.0×10⁶ N/m² and at about 8.9×10⁷ N/m² was about 0.35 cm and about0.2 cm, respectively.

For the larger boards, each sample/mixture/blend (about 105 g for eachsample/mixture) of CCP, CCP/ASCCF/WG, CCP/ASCCF/RN, or CCP/ASCCP/PU wascompression-molded at about 160° C. to form each board. It is noted thatin order to prepare the larger boards at the same pressures (at about4.0×10⁶ and 8.9×10⁷ N/m²) used for molding the small bars, compressionforces of about 1.3×10⁵ N (30,000 lb_(f)) and about 2.7×10⁶ N (616,000lb_(f)) should be applied.

However, the exemplary hot-press used was capable of a maximumcompression force of about 2×10⁵ N. Therefore, the larger boards wereprepared at just one compression pressure, 4.0×10⁶ N/m². The dimensionsof the larger boards after compression molding were about 21 cm×14cm×0.4 cm. Molding time to prepare small bars and larger boards wasabout 20 minutes, except for those cases where the compositescontained/included PU binder, where about 7 minutes of molding time wasutilized.

TABLE 8 The composite components used to prepare small bars: CompositesRatio (% wt) CCP 100 CCP/ASCCF 90/10 CCP/WG 95/5, and 90/10 CCP/RN 95/5,and 90/10 CCP/PU^(a) 90/10 CCP/ASCCF/WG 85/10/5, and 80/10/10CCP/ASCCF/RN 85/10/5, and 80/10/10 CCP/ASCCF/PU^(a) 80/10/10 ^(a)In thecase of the PU binder, about 10-15 wt % of the binder with respect tototal weight of the composites was recommended to bind the coconut fiberand pith. Thus, only about 10 wt % of PU binder was used to preparethose composites.

Analytical Techniques:

Mechanical Property Testing:

The molded bars were used for a three-point bending test performedaccording to the standard test methods for flexural properties ofunreinforced and reinforced plastics and electrical insulatingmaterials, ASTM D790-02. The molded specimens were kept in a desiccatorcontaining Drierite® desiccant (about 30% relative humidity) for atleast 3 days before testing. The tests were conducted on acomputer-interfaced Instron 1011 with about a 50 N load cell. The rateof crosshead motion was about 1 mm/min, while the data acquisition ratewas about 10 points per second. Four replicates were performed for eachcomposite.

In the case of the larger boards, modulus of rupture (“MOR”), modulus ofelasticity (“MOE”) and tensile strength parallel to surface (“TS”) weremeasured according to the standard test methods for evaluatingproperties of wood-based fiber and particle panel materials, ASTMD1037-99 using the Instron 1011. The specimens were kept in thedesiccator for at least 3 days before the measurements of MOR, MOE andTS. For MOR and MOE measurements, about a 500 N load cell was used witha rate of crosshead motion of about 2 mm/min. For the TS measurements,about a 500N load cell was used for the CCP, CCP/ASCCF/WG andCCP/ASCCF/PU composites, and about a 5 kN load cell was used for theCCP/ASCCF/RN composites, both with a rate of crosshead motion of about 4mm/min. Three to five specimens were tested for each composite.

Nail-Driving Test:

This test was performed to examine the toughness of the boards whennails were driven through them. The fabricated/manufactured CCP,CCP/ASCCF/WG, CCP/ASCCF/RN, and CCP/ASCCF/PU larger boards were cut toabout 5×5 cm (2×2 inch) size. Nails of about 2.18 mm in diameter weredriven into the boards substantially perpendicular to the plane at thecenter of the boards. Twenty replicates were performed for each typefrom five boards. The number of samples that cracked or otherwisefailed, and the description of the failures are reported below.

Water Absorption and Thickness Swelling of Particleboard:

The water absorption (“WA”) and thickness swelling (“TSW”) tests of thelarger boards were carried out according to ASTM D1037-99. The method A:2 plus about 22-hour submersion period in water was used for the testingto provide information on the short term and longer term WA and TSWvalues. The specimens were cut to about 5×5 cm (2×2 inch) from thelarger boards and then conditioned in a chamber containing a saturatedmagnesium nitrate solution at about 20° C. for about 48 hours tomaintain a relative humidity of about 55%. Three specimens from each ofthree different larger boards were used for the testing. The WA and TSWvalues are expressed as a percent for the specimens after about 2 hours,and after an additional period of about 22 hours submersion. Thepercentage of WA and TSW was calculated as follows:

WA(%)=[(W _(s) −W ₀)/W ₀]×100  (Equation 1)

TSW(%)=[(T _(s) −T ₀)/T ₀]×100  (Equation 2)

where W_(s) and T_(s) are weight and thickness of a specimen aftersubmersion, respectively. W₀ and T₀ are initial weight and thickness ofa specimen before submersion, respectively.

All specimens were horizontally submerged in distilled water maintainedat a temperature of about 20° C. After about a 2 hour submersion, eachspecimen was removed from the water and put on a plastic rack to removethe excess surface water for about 10 minutes. At the end of this time,the weight and thickness of the specimen was immediately measured. Then,the specimen was submerged in fresh water for an additional period ofabout 22 hours, and the above procedure for removing excess water,weighing and measuring was repeated.

Thermo-Gravimetric Analysis (TGA):

TGA was used to investigate thermal decomposition of the prepared largerparticleboards. TGA was performed on a TA Instruments Hi-Res 2950instrument equilibrated at about 60° C., followed by a ramp to about800° C. at about 20° C./minute in air with a flow rate of about 60mL/min.

Results and Discussion:

Mechanical Property of Small Bar Composites:

To investigate the effect of compression pressure on the mechanicalproperties, the small molded bars of the composites were prepared at twodifferent molding pressures: about 4.0×10⁶ N/m² (molding condition #1),and about 8.9×10⁷ N/m² (molding condition #2). A comparison of themechanical properties of CCP, CCP/ASCCF, CCP/binder, andCCP/ASCCF/binder composites are summarized in Table 9 below. The firstfailure stress values are the stresses at which the WG matrix began tocrack, and are illustrated in FIGS. 11A-H (arrow sign).

Without a binder, it is noted that the modulus (GPa) of thesubstantially pure CCP molded at the higher pressure of 8.9×10⁷ N/m²(molding condition #2) increased by about 7 times compared to the CCP atmolding condition #1, and that the strength (MPa) of the CCP at moldingcondition #2 increased by about 9 times compared with the CCP molded atthe lower pressure of 4.0×10⁶ N/m² (molding condition #1—Table 9 below).These large changes are most likely the result of high lignin andphenolic content (about 45%) in coconut pith, and at temperatures aboveabout 140° C., the lignin and phenolic substances can melt and act likea thermosetting adhesive. Thus, they might act as an intrinsic resinadhesive, resulting in an increase in the modulus and strength at thehigher molding pressure.

As shown in Table 9, the modulus (GPa) and strength (MPa) of all thecomposites relative to one another prepared at the higher compressionpressure (molding condition #2) significantly increased compared withthose consolidated with lower pressure (molding condition #1). However,the elongation of all molded composites relative to one anotherdecreased at the higher compression pressure (Table 9).

The effect of binder content on the mechanical properties of thefabricated particleboards/composites was also evaluated. Two differentbinder loadings were used, about 5 wt % and about 10 wt %, with respectto total weight of composites (Table 9).

In all cases, the composites with 10 wt % binder content providedsuperior results for strength and elongation compared to the compositesconsolidated with 5 wt % binder content. The effect of binder content onthe modulus was not as significant, but the composites with 10 wt %binder generally had greater than or equal modulus values than thecorresponding composites with 5 wt % binder.

The addition of the ASCCF into the CCP, CCP/WG, CCP/RN or CCP/PUenhanced the mechanical properties of the composites compared with thecorresponding composites without ASCCF (Table 9). Thus, the ASCCF playeda role as reinforcement in the composites, thereby improving themechanical properties of the composites. Among the three binders tested,the composites with RN binder had the most desirable properties in mostcases. However, the CCP/ASCCF/PU binder had a very graceful failuremode, achieving very similar maximum strength as the CCP/ASCCF/RNcomposite, but with greater ductility.

FIGS. 11A-H show the stress-strain curves of the small bar composites,which were compressed at about 160° C. with about 8.9×10⁷ N/m² for about20 minutes, except for the CCP/PU and CCP/ASCCF/PU composites, where amolding time of about 7 minutes was used. There was substantially noductile behavior in the stress-strain curves of the binderless CCP,CCP/WG, CCP/RN, and CCP/PU, while the composites reinforced with ASCCFeither with or without a binder showed ductile failure behavior. In thecomposites reinforced with ASCCF, the first failure is indicated by anarrow, and in several cases the maximum failure is at higher stress andlarger strain.

TABLE 9 Mechanical properties of small bars based on coconut materials:Molding condition #1^(a,b) Molding condition #2^(a,b) (molding pressure= 4.0 × 10⁶ N/m²) (molding pressure = 8.9 × 10⁷ N/m²) First failureFirst failure Composite stress stress type Modulus (Max. stress)Elongation Modulus (Max. stress) Elongation (Ratio, % wt) (GPa) (MPa)(%) (GPa) (MPa) (%) CCP 0.57 ± 0.08  3.71 ± 0.27 1.00 ± 0.17 3.83 ± 0.1131.76 ± 0.98 0.86 ± 0.03 (100)  (3.71 ± 0.27) (1.00 ± 0.17) (31.76 ±0.98) (0.86 ± 0.03) CCP/ASCCF 0.65 ± 0.05 12.25 ± 0.62 2.33 ± 0.11 3.91± 0.59 40.05 ± 1.11 0.88 ± 0.10 (90/10) (14.34 ± 1.73) (3.06 ± 0.18)(41.89 ± 1.16) (4.32 ± 0.20) CCP/WG 0.87 ± 0.09  6.05 ± 0.72 1.00 ± 0.103.44 ± 0.15 30.97 ± 1.41 0.96 ± 0.07 (95/5)  (6.05 ± 0.72) (1.00 ± 0.10)(30.97 ± 1.41) (0.96 ± 0.07) CCP/WG 1.20 ± 0.08  9.20 ± 1.38 1.07 ± 0.073.83 ± 0.10 40.57 ± 1.47 1.03 ± 0.07 (90/10)  (9.20 ± 1.38) (1.07 ±0.07) (40.57 ± 1.47) (1.03 ± 0.07) CCP/RN 1.76 ± 0.09 25.09 ± 1.11 1.48± 0.05 3.75 ± 0.11 43.44 ± 1.88 1.22 ± 0.14 (95/5) (25.09 ± 1.11) (1.48± 0.05) (43.44 ± 1.88) (1.22 ± 0.14) CCP/RN 2.13 ± 0.10 38.87 ± 1.861.76 ± 0.08 3.59 ± 0.12 46.28 ± 1.75 1.33 ± 0.06 (90/10) (38.87 ± 1.86)(1.76 ± 0.08) (46.28 ± 1.75) (1.33 ± 0.06) CCP/PU 1.13 ± 0.06 14.25 ±0.80 1.37 ± 0.05 3.03 ± 0.11 30.62 ± 1.37 1.06 ± 0.04 (90/10) (14.25 ±0.80) (1.37 ± 0.05) (30.62 ± 1.37) (1.06 ± 0.04) CCP/ASCCF/WG 1.29 ±0.09 14.50 ± 0.91 1.75 ± 0.13 3.95 ± 0.16 41.13 ± 1.61 1.07 ± 0.06(85/10/5) (17.84 ± 1.69) (3.10 ± 0.15) (43.38 ± 1.84) (3.56 ± 0.09)CCP/ASCCF/WG 1.45 ± 0.12 22.07 ± 0.85 1.94 ± 0.34 4.00 ± 0.14 45.60 ±1.58 1.09 ± 0.10 (80/10/10) (27.11 ± 1.99) (3.25 ± 0.17) (47.25 ± 2.01)(4.09 ± 0.12) CCP/ASCCF/RN 2.05 ± 0.10 28.02 ± 1.56 1.52 ± 0.20 3.69 ±0.10 47.87 ± 2.07 1.34 ± 0.04 (85/10/5) (36.68 ± 2.19) (2.32 ± 0.26)(47.87 ± 2.07) (1.34 ± 0.04) CCP/ASCCF/RN 2.21 ± 0.10 32.86 ± 1.08 1.87± 0.18 3.51 ± 0.09 50.78 ± 1.86 1.48 ± 0.08 (80/10/10) (41.20 ± 1.22)(1.57 ± 0.15) (50.78 ± 1.86) (1.48 ± 0.08) CCP/ASCCF/PU 1.40 ± 0.1324.98 ± 2.30 1.83 ± 0.10 3.26 ± 0.11 40.29 ± 1.29 1.45 ± 0.16 (80/10/10)(34.27 ± 0.27) (6.36 ± 0.37) (51.73 ± 2.15) (5.73 ± 0.22) ^(a)Moldingcondition: about 160° C., at about 20 minutes, except for compositeshaving PU binder where molding time of about 7 minutes was used. ^(b)Aplus/minus value (±) is a sample standard deviation. Five specimens wereprepared from one pressing in the same mold.

Mechanical Property of Larger Boards:

The modulus of rupture (“MOR”), modulus of elasticity (“MOE”), andtensile strength parallel to the surface (“TS”) were measured by ASTMD1037-99. The measurements for CCP, CCP/ASCCF/WG, CCP/ASCCF/RN, andCCP/ASCCF/PU boards prepared at about 160° C. with about 4.0×10⁶ N/m²compression pressure are presented in Table 10 below. This compressionpressure substantially matches molding condition #1 for the small bars.The boards with fiber and binder all contained about 10 wt % fiber andabout 10 wt % binder, and were consolidated for about 20 minutes, exceptfor CCP/ASCCF/PU composites, where about 7 minutes consolidation wasused. It can be seen that CCP/ASCCF/RN particleboard had the highestmechanical properties compared with others, which is in agreement withthe mechanical property results found in the small bar composites wherethe RN-bound composites showed better mechanical properties than WG- andPU-bound composites. Interestingly, the mechanical properties of theWG-bound particleboard were comparable to those of the board preparedwith the commercial PU binder.

TABLE 10 The density and mechanical properties of the CCP-basedparticleboards: Board Particleboard density Formulation MOE^(a) MOR^(a)TS^(b) type (kg/m³) (wt %) (GPa) (MPa) (MPa) CCP 756 ± 16 100 0.28 ±0.14 1.4 ± 0.10 0.77 ± 0.15 CCP/ASCCF/WG 797 ± 5  80/10/10 0.68 ± 0.107.8 ± 1.13 2.93 ± 0.17 CCP/ASCCF/RN 810 ± 8  80/10/10 1.73 ± 0.49 13.1 ±2.15 6.00 ± 0.17 CCP/ASCCF/PU 788 ± 10 80/10/10 0.75 ± 0.20 6.8 ± 0.433.10 ± 0.37 ^(a)MOE is modulus of elasticity, MOR is modulus of rupturewhich is maximum stress. ^(b)For tensile strength (TS), dog-bone samplescut from the larger boards were used.

The MOE and MOR of manufactured particleboards were also compared withthe minimum requirements of mechanical properties (MOE and MOR) forcommercial particleboard manufacturing, which is specified by theAmerican National Standard Institute (ANSI), ANSI A208.1-1999 forparticleboard. In the ANSI Standard A208.1, the particleboard grades areidentified by a letter designation, followed by a hyphen and a digit orletter. The first letter designation indicates density classes. Forinstance, the letter “H” means high density (generally above 800 kg/m³),“M” means medium density (generally between 640-800 kg/m³), and “L”means low density (generally less than 640 kg/m³). The second digitdesignation indicates the grade identification within a particulardensity or product description.

The particleboards listed in Table 10 were compared to the mediumdensity (M) particleboard standard, even though the density ofWG/ASCCF/RN was slightly above 800 kg/m³. Table 11 below representsgeneral use and grades of the medium density particleboards, as well asmechanical property (MOE and MOR) requirements for the particleboardaccording to the ANSI A208.1.

TABLE 11 General use, grades, and mechanical property requirements formedium density particleboards according to the ANSI A208.1: Grade MOE(GPa) MOR (MPa) General use M-1 1.725 11.0 Commercial M-S 1.900 12.5Commercial M-2 2.250 14.5 Industrial M-3 2.750 16.5 Industrial andinterior stair tread

FIGS. 12A-B show MOE (FIG. 12A) and MOR (FIG. 12B) of CCP, CCP/ASCCF/WG,CCP/ASCCF/RN, and CCP/ASCCF/PU particleboards compared with the minimumrequirement of MOR and MOE for the M-1 particleboard according to theANSI A208.1. The horizontal solid lines indicate the minimum MOE (1.725GPa), and MOR (11.0 MPa) requirements for the M-1 grade particleboard,respectively. From FIGS. 12A-B, the CCP, CCP/ASCCF/WG, and CCP/ASCCF/PUboards did not meet the minimum requirement of MOE and MOR. However, theCCP/ASCCF/RN board did meet the minimum requirements for MOE and MOR ofM-1 grade particleboard.

The mechanical properties of the small bars and the largerparticleboards determined according to ASTM D790-02 and ASTM D1037-99,respectively, are summarized in Table 12 below. The small bars molded atthe higher pressure (8.9×10⁷ N/m²) had modulus and strength at least 1.5times higher than the ones pressed at the lower pressure (4.0×10⁶ N/m²).Therefore, it is reasonable to predict that if the larger particleboardswere molded at the higher pressure, superior results for the mechanicalproperties (MOE and MOR) would also be obtained.

TABLE 12 Mechanical properties of the small bars and largerparticleboards investigated according to ASTM D790-02 and ASTM D1037-99:Molding condition #2 Molding condition #1 (molding pressure = (moldingpressure = 4.0 × 10⁶ N/m²) 8.9 × 10⁷ N/m²) Small bar Small bar MaximumLarger particleboard Maximum Composite type Modulus^(a) Strength^(a)MOE^(b) MOR^(b) Modulus^(a) Strength^(a) (Ratio, % wt) (GPa) (MPa) (GPa)(MPa) (GPa) (MPa) CCP 0.57 ± 0.08  3.71 ± 0.27 0.28 ± 0.13 1.37 ± 0.193.83 ± 0.11 31.76 ± 0.98 (100) CCP/WG 1.20 ± 0.08  9.20 ± 1.38 — — 3.83± 0.10 40.57 ± 1.47 (90/10) CCP/RN 2.13 ± 0.10 38.87 ± 1.86 — — 3.59 ±0.12 46.28 ± 1.75 (90/10) CCP/PU 1.13 ± 0.06 14.25 ± 0.80 — — 3.03 ±0.11 30.62 ± 1.37 (90/10) CCP/ASCCF/WG 1.45 ± 0.12 27.11 ± 1.99 0.68 ±0.10 7.78 ± 1.13 4.00 ± 0.14 47.25 ± 2.01 (80/10/10) CCP/ASCCF/RN 2.21 ±0.10 41.20 ± 1.22 1.73 ± 0.49 13.10 ± 2.15  3.51 ± 0.09 50.78 ± 1.86(80/10/10) CCP/ASCCF/PU 1.40 ± 0.13 34.27 ± 0.27 0.75 ± 0.20 6.82 ± 0.433.26 ± 0.11 51.73 ± 2.15 (80/10/10) ^(a)Mechanical properties of smallbars investigated by a three-point bending test performed according tothe ASTM D790-02. ^(b)Mechanical properties of larger particleboardsinvestigated by a bending test performed according to the ASTM D1037-99.

Nail-Driving Test:

For certain applications (e.g., indoor applications), particleboards arenailed for installation. Thus, the behavior of the particleboards duringnail driving was examined. Qualitative tests were performed, and thenumber of failed particleboards is reported in Table 13 below.

Additionally, FIGS. 13A-H show particleboard images after thenail-driving test. In the case of boards without the addition of ASCCF,85% of the binderless CCP boards failed. In the CCP/WG and CCP/RN boardsat the ratio of 90/10 by weight, the percentage of failures is 10% and15%, respectively. In failed CCP boards, the boards broke, or thesurface of the boards peeled in flakes as illustrated in FIGS. 13A and13B. The CCP/WG boards that failed broke, but did not substantially peel(FIG. 13C). In the case of CCP/RN boards, the failure of the boards wasprimarily due to brittleness (FIG. 13D). It is believed that theaddition of the high percentage of the RN binder made the boards toobrittle. Generally, the amount of the methyl diisocyante (“MDI”)-basedisocyanate binder used in production of particleboards is less thanabout 10%, preferably about 6%. See, e.g., U.S. Pat. No. 6,692,670, theentire contents of which is hereby incorporated by reference in itsentirety.

In the CCP/PU boards, no failures were observed. No failures wereobserved in any of the boards reinforced with ASCCF.

TABLE 13 Number of failed particleboards after the nail-driving test:Particleboard Number of tested Number of failed Failure percent typesamples samples (%) CCP 20 17 85 CCP/WG 20 2 10 CCP/RN 20 3 15 CCP/PU 200 0 CCP/ASCCF/WG 20 0 0 CCP/ASCCF/RN 20 0 0 CCP/ASCCF/PU 20 0 0

Water Absorption and Swelling Characteristics of the Particleboard:

The water absorption and the thickness swelling of particleboardsgenerally are important properties for evaluating their stabilitycompared to realistic conditions during construction and subsequentusage. The water absorption (WA) and thickness swelling (TSW) ofCCP/ASCCF/WG, CCP/ASCCF/RN, and CCP/ASCCF/PU boards were evaluated interms of percentage values calculated by equations (1), and (2) above,respectively. The results of the percent water absorption (% WA) andthickness swelling (% TSW) are given in Table 14.

TABLE 14 Water absorption and thickness swelling of the particleboard:Percent water absorption Percent thickness swelling Particleboard (% WA)(% TSW) type After 2 h After 24 h After 2 h After 24 h CCP/ 110.82 ±6.51    135 ± 3.84 51.03 ± 2.37 59.40 ± 4.18 ASCCF/WG CCP/ 13.97 ± 1.3438.89 ± 1.74  9.34 ± 1.38 15.53 ± 1.91 ASCCF/RN CCP/ 17.07 ± 2.08 42.21± 1.15 11.20 ± 1.46 18.01 ± 1.21 ASCCF/PU

The WA and TSW of CCP board could not evaluated because when the CCPspecimen was soaked in water, it gradually decomposed into CCPparticles, primarily due to the absence of binder. From Table 14, it canbe seen that the particleboard using the WG binder provided the greatestvalues in % WA and % TSW in both short (2 hour) and long (2 plus 22hour) terms of submersion. In the case of CCP/ASCCF/RN and CCP/ASCCF/PU,the % WA and % TSW values were comparable, and were much lower thanthose in the WG bonded particleboard.

Lignocellulosic materials such as coconut pith and coconut fiber consistof cellulose, hemicelluloses, and lignin, where there are large numbersof hydroxyl groups (—OH). These hydrophilic materials typically absorblarge amounts of water and consequently swell. However, a high degree ofreaction between a binder and the hydroxyl groups in the lignocellulosicmaterials can potentially reduce the water absorption and swelling bymaking the material more hydrophobic. In the case of the RN binder,isocyanate groups have high reactivity with hydroxyl groups of CCP. ThePU binder consisting of polyol and polyisocyanate hardener can reactwith itself and the OH groups to form a crosslinked structure with theCCP. The WG binder consists mainly of proteins that absorb water. As aresult, the RN- and PU-bound particleboards have much lower % WA and %TSW than the WG-bound particleboard.

Thermo-Gravimetric Analysis (TGA):

The thermal stability of particleboards generally is an importantproperty for evaluating fire resistance. TGA was used to investigate thethermal decomposition temperature of the particleboards. Weight loss andcorresponding first derivative of weight loss thermogram (DTG) curves ofthe composites are shown in FIG. 14. Table 15 also presents thermaldecomposition temperature (T_(d)) at 5 wt % loss and temperature ofmaximum decomposition rate (T_(p)) at the second step of decompositionin DTG curves. The TGA curves of the particleboards showed a similarpattern, where there are four main weight-loss stages. The first stagewith a slight weight loss below about 130° C. of the particleboards wascaused by evaporation of absorbed water in the boards. In general, threemain degradation stages can be attributed to pyrolysis and evaporationof the pyrolytic products.

From Table 15, the CCP-based particleboards glued with the bindersprovided higher T_(d) and T_(p) than the binderless CCP particleboardbecause a presence of chemical bonding between the binders and eitherCCP or ASCCF. Among the three types of binders, the RN-boundparticleboard showed the highest thermal stability on account of a highdegree of reaction between isocyanate groups of the RN binder andhydroxyl groups on the surface of CCP or ASCCF.

TABLE 15 Thermal decomposition temperature (T_(d)) and temperature ofmaximum decomposition rate (T_(p)) of the composites: T_(d) at T_(p) atthe second step of Composite type 5 wt % loss (° C.) decomposition (°C.) CCP 134.1 269.7 CCP/WG 197.2 280.2 CCP/RN 229.7 305.2 CCP/PU 198.0289.8

Conclusions:

The small bars of CCP, and WG-, RN-, and PU-bound CCP composites wereprepared to investigate the effects of molding pressure, binder contentand binder type on the mechanical properties. It is noted that excellentproperties were obtained with high pressure molded bars. It was alsofound that the addition of the ASCCF at about 10 wt % fiber into thelarger particleboards bound with binders enhanced the mechanicalproperties. At high binder content, the properties of composites with orwithout ASCCF improved. Among the three binders, RN generally had themost desirable mechanical properties. Compared with the CCP compositebars with the commercial PU, the WG-bound CCP bars provided comparableor higher mechanical properties. As such, the WG has a potential to be apromising binder for particleboard production.

The ASCCF-reinforced CCP particleboard bound with RN binder showedbetter mechanical (MOE, MOR, and TS) and physical (WA % and TSW %)properties, as well as thermal stability than those bound with WG andPU. At the low molding pressure, the CCP/ASCCF/RN particleboard met theminimum MOE and MOR requirements for M-1 grade particleboard accordingto the ANSI A208.1-1999. From the preliminary mechanical propertyresults of small bar composites molding at the high pressure, whichshowed an increase in the mechanical properties, it is expected that itis possible that the properties CCP/ASCCF/WG and CCP/ASCCF/PU pressed atthe higher molding pressure will greatly improve and exceed the minimumcommercial requirements for industrial particleboard production.

Example 5 Composites/Particleboards Containing Bagasse Fibers

Materials:

RUBINATE®1780 (“RN”), a methylene diphenyl diisocyanate binder, wassupplied by Huntsman Polyurethanes, USA.(3-triethoxysilylpropyl)-t-butylcarbamate (masked isocyanate silane orMISO) was purchased from Gelest Inc., USA. The sodium hydroxide wassupplied by Fisher Scientific, USA. Acetone was obtained from J.T.Baker, USA.

It is again noted that other fibers or lignocellulosic fibers/materialsmay be used in lieu of the bagasse in the systems, processes, methodsand examples of the present disclosure.

Fiber Treatments:

Bagasse fibers were cut into about 40 mm lengths, and were dried in avacuum oven at about 50° C. for about 2 hours (moisture content about4.5%). Some of the bagasse fiber was then subjected to fiber treatments(e.g., surface treatments), as described below.

Alkali Treatment (Mercerization):

Samples of dried bagasse fibers were soaked in about 5% w/v sodiumhydroxide solution in water for about 4 hours at room temperature, thenwashed thoroughly with distilled water until the rinse solution reacheda pH of about 7. Each batch of alkaline-treated fibers was then dried atroom temperature for about 12 hours, and then dried in a vacuum oven atabout 50° C. for about 2 hours (moisture content about 4.5%).

Silane Treatment:

(3-triethoxysilylpropyl)-t-butylcarbamate was dissolved in about a 50/50v/v solution of water and acetone (about 0.1 volume % silane in thesolution). The pH was adjusted to about 4 with acetic acid, stirring thesolution continuously for about 30 minutes. Some of the driedalkali-treated fibers were then soaked in the solution for about 2hours.

The fibers were then removed from the silane solution, and the solventwas allowed to evaporate in an air stream at room temperature for about2 hours. The fibers were dried in a vacuum oven at about 50° C. forabout 12 hours (moisture content about 4.5%).

Again, it is noted that the present disclosure contemplates that thesilane (e.g., masked isocyanate functional silane) may beincorporated/contacted and/or mixed/blended with the fibers, materials,mixtures, blends and/or samples in a variety of ways, and at variousdifferent steps in the fabrication process. For example, the silane(MISO) may be incorporated into the sodium hydroxide solution discussedabove, and the fibers may be simultaneously soaked in the NaOH and thesilane solution, followed by the drying and composite preparation (e.g.,mixing/incorporating with binder and/or molding) steps.

Alternatively, the silane (MISO) may be deposited (e.g., via liquidspraying or the like) onto the lignocellulosic fibers/materials (e.g.,after the NaOH treatment), and then the silane-treated fibers may bemixed/incorporated with a binder (if desired) and thenmolded/fabricated. It is noted that the lignocellulosic fibers/materialsmay be mixed/blended with the binder material (if desired) before,during, or after the silane treatment (e.g., silane treatment via liquidspraying or the like). For example, it is noted that the binder materialmay be contacted/deposited (e.g., via liquid spraying or the like) ontoand/or mixed/blended (e.g., as a liquid or solid) with thelignocellulosic fibers/materials before, during or after the silanetreatment (e.g., silane liquid spraying treatment, substantiallysolid-silane mixing step, and/or after silane solution soakingtreatment, etc.).

In certain embodiments, the alkali-treatment step (if desired) may befollowed by a silane-treatment step where the MISO silane ismixed/contacted with the other components (e.g., fibers/materials andbinder) in substantially one step (e.g., a solids mixing step withMISO/MISO powder and/or binder, and/or a liquid spray treatment stepwith MISO and/or binder, etc.), followed then by a molding/fabricationstep. As noted, the silane-treatment step(s) could have severalvariations, such as, for example, a silane-treatment step where thecomponents (fibers/materials, MISO silane and/or binder) aremixed/blended together as solids, and/or as a step where the MISO silaneand/or binder (if desired) is sprayed onto the lignocellulosicfibers/materials (and other solids) as a liquid.

Composite Preparation:

Acetone was mixed with the RN binder to reduce its viscosity. Ingeneral, the ratio of the RN binder to acetone for preparation of thebinder solution was about 1:2 wt/vol. The binder solution and the alkaliand silane treated bagasse fibers were then mechanically mixed for about5 minutes.

The mixtures (e.g., mixtures obtained via mechanical mixing or thelike), blends or samples (about 70 g total for each sample/mixture) ofthe alkali and silane treated bagasse fibers, along with the RN binder,were then compression-molded at about 160° C. for about 20 minutes, andat about 4×10⁶ N (about 25,000 lb_(f)), in a mold to form about210×140×2.74 mm boards.

For the mixtures, blends or samples that were fabricated into the boardslisted in Table 16 below, the weight ratio of bagasse fiber to RN wasabout: (i) 80/20, or (ii) 90/10 by weight percent.

Three Point Bending Tests:

Each fabricated board was cut into samples with dimension of about 117mm×50 mm×2.74 mm. Modulus of Rupture (“MOR”) and modulus of elasticity(“MOE”) were measured by three point bending tests with an Instron-1011.The tests were performed with about a 500N load cell, and the crossheadspeed was about 2 mm/minute. The testing procedures were conductedaccording to ASTM D 1037-99, as specified in the ANSI A208.1-1999standard. The results are displayed in Table 16 below.

TABLE 16 Bagasse-based particleboard testing results: Bagasse SampleMass % RN Mass % MOE, GPa MOR, MPa 1A 80 20 2.3 34.9 2A 80 20 2.3 34.83A 80 20 2.5 37.7 Average 2.37 +− 0.115 35.8 +− 1.65 (samples 1A-3A) 1B90 10 2.9 33.3 2B 90 10 2.8 29.6 3B 90 10 2.6 29.9 4B 90 10 3.2 32.8Average 2.88 +− 0.25 31.4 +− 1.92 (samples 1B-4B)

Discussion:

An exemplary stress strain curve for sample 2A is shown in FIG. 15. Itis noted that the stress-strain curves for samples 1A, 2A and 3A lookedsubstantially the same.

According to the ANSI A208.1-1999 standard, shown in Table 11 above, theMOE of the fabricated bagasse fiberboard reached the M-2 grade, and theMOR far exceeded all requirements.

Although the systems, assemblies and methods of the present disclosurehave been described with reference to exemplary embodiments thereof, thepresent disclosure is not limited to such exemplary embodiments and/orimplementations. Rather, the systems, assemblies and methods of thepresent disclosure are susceptible to many implementations andapplications, as will be readily apparent to persons skilled in the artfrom the disclosure hereof. The present disclosure expressly encompassessuch modifications, enhancements and/or variations of the disclosedembodiments. Since many changes could be made in the above constructionand many widely different embodiments of this disclosure could be madewithout departing from the scope thereof, it is intended that all mattercontained in the drawings and specification shall be interpreted asillustrative and not in a limiting sense. Additional modifications,changes, and substitutions are intended in the foregoing disclosure.Accordingly, it is appropriate that the claims be construed broadly andin a manner consistent with the scope of the disclosure.

1. A method for fabricating a biocomposite, comprising: treating aportion of a lignocellulosic material with a solution for removingsurface impurities; and treating a portion of the lignocellulosicmaterial with an adhesion promoter, wherein the adhesion promoterincludes a masked adhesion promoter.
 2. The method of claim 1, furthercomprising drying the lignocellulosic material after treating theportion of the lignocellulosic material with the solution for removingsurface impurities.
 3. The method of claim 1, wherein the step oftreating a portion of a lignocellulosic material with a solution forremoving surface impurities includes at least one of soaking,contacting, spraying, depositing, mixing or blending the portion of thelignocellulosic material with the solution for removing surfaceimpurities.
 4. The method of claim 1, further comprising drying thelignocellulosic material after treating the portion of thelignocellulosic material with the masked adhesion promoter.
 5. Themethod of claim 1, wherein the step of treating a portion of alignocellulosic material with a masked adhesion promoter includessoaking, contacting, spraying, depositing, mixing or blending a portionof a lignocellulosic material with a masked adhesion promoter.
 6. Themethod of claim 1, further comprising demasking the masked adhesionpromoter.
 7. The method of claim 1, further comprising treating thelignocellulosic material with a binder to form a composite preparation.8. The method of claim 7, wherein the binder includes a wheatgluten-based binder.
 9. The method of claim 7, further comprising curingthe composite preparation.
 10. The method of claim 9, wherein the stepof curing includes curing above room temperature.
 11. The method ofclaim 1, wherein the solution for removing surface impurities includesan alkali solution.
 12. The method of claim 1, wherein the maskedadhesion promoter includes a masked functional silane coupling agent.13. The method of claim 1, wherein the lignocellulosic material includesbagasse.
 14. The method of claim 1, wherein the lignocellulosic materialincludes wood.
 15. A method for fabricating a biocomposite comprising:treating a portion of a lignocellulosic material with an adhesionpromoter, wherein the adhesion promoter includes a masked adhesionpromoter; and molding the lignocellulosic material.
 16. The method ofclaim 15, further comprising demasking the masked adhesion promoter. 17.The method of claim 15, further comprising treating the lignocellulosicmaterial with a binder to form a composite preparation.
 18. The methodof claim 17, wherein the binder includes a wheat gluten-based binder.19. The method of claim 15, further comprising: drying thelignocellulosic material after treating; and curing the compositepreparation.
 20. The method of claim 15, wherein the masked adhesionpromoter includes a masked functional silane coupling agent.
 21. Themethod of claim 15, wherein the lignocellulosic material includes atleast one of a coconut material, a bagasse material, a wood material, ahemp material, a kenaf material, a jute material and a cereal strawmaterial.
 22. A material mixture for use as a component in a curedbiocomposite, the material mixture comprising at least onelignocellulosic material treated with a masked functional silanecoupling agent.